comments

src/decode/cmds.rs

@@ -7,6 +7,7 @@ use crate::decode::codecs::Decoder;
 use crate::decode::codecs;
 
 pub fn spawn(metadata: Arc<util::Metadata>) -> Result<(impl Decoder, impl Decoder), Box<dyn Error>> {
+    // create appropriate decoder implementation for input codec
     let v = match metadata.video.codec {
         Some(util::VideoCodec::H264) => codecs::video::new_h264(metadata.clone())?,
         _ => {return Err(Box::new(util::DecoderError::CodecNotImplemented));}
@@ -19,9 +20,10 @@ pub fn spawn(metadata: Arc<util::Metadata>) -> Result<(impl Decoder, impl Decode
 }
 
 pub fn handle_decoder(mut decoder: impl Decoder, c_in: mpsc::Receiver<util::NALUPacket>, c_out: mpsc::Sender<util::RawMedia>, c_err: mpsc::Sender<Box<dyn Error + Send + Sync>>) {
+    // take stdin and stdout for process to read from and write to on different threads
     let stdin = decoder.stdin();
     let stdout = decoder.stdout();
-    let raw_buff_size = decoder.raw_buff_size();
+    let raw_buff_size = decoder.raw_buff_size(); // determined by input parameters and codec
     let raw_sample_type = decoder.media_type();
     let c_err2 = c_err.clone();
     thread::spawn(move || {

src/decode/codecs/audio.rs

@@ -30,9 +30,10 @@ impl Decoder for AACDecoder {
 }
 
 pub fn new_aac(metadata: Arc<util::Metadata>) -> Result<AACDecoder, Box<dyn Error>> {
+    // faad for AAC -> raw PCM 16-bit little-e, piped
     let cmd = Command::new("faad")
         .args(["-f", "2", "-w", "-q", "-"])
         .stdin(Stdio::piped()).stdout(Stdio::piped()).spawn()?;
-    let bytes_per_sample_chunk = (metadata.audio.samplerate * 2 * metadata.audio.channels as u32) as usize;
+    let bytes_per_sample_chunk = (metadata.audio.samplerate * 2 * metadata.audio.channels as u32) as usize; // channels * 2 bytes per sample, * samplerate for bytes per second
     return Ok(AACDecoder {cmd: cmd, raw_buff_size: bytes_per_sample_chunk, raw_sample_type: util::RawMediaType::PCM16LE})
 }

src/decode/codecs/mod.rs

@@ -20,11 +20,14 @@ pub trait Decoder {
     fn media_type(&self) -> util::RawMediaType;
 }
 
+// write to decoder
 fn write_nalu(cmd_in: &mut ChildStdin, nalu: util::NALUPacket) -> Result<(), Box<dyn Error + Send + Sync>> {
-    cmd_in.write_all(nalu.packet_data.as_slice())?;
+    cmd_in.write_all(nalu.packet_data.as_slice())?; // nalus should already be in bytestream
+                                                    // format, send as is
     Ok(())
 }
 
+// read from decoder
 fn read_raw(cmd_out: &mut ChildStdout, raw_buff_size: usize, media_type: util::RawMediaType) -> Result<util::RawMedia, Box<dyn Error + Send + Sync>> {
     let mut raw_buff = vec![0u8; raw_buff_size];
     match cmd_out.read_exact(raw_buff.as_mut_slice()) {
@@ -39,11 +42,14 @@ pub fn read_nalu_loop(mut cmd_in: ChildStdin, c_in: mpsc::Receiver<util::NALUPac
     loop {
         let nalu = match c_in.recv() {
             Ok(x) => x,
-            Err(err) => {drop(cmd_in); thread::park();return}
+            Err(err) => {drop(cmd_in); thread::park();return} // drop cmd_in to signal EOF to
+                                                              // decoder, letting the decoder close
+                                                              // stdout when done
         };
         match write_nalu(&mut cmd_in, nalu) {
             Ok(_) => (),
-            Err(err) => {util::thread_freeze(c_err, err); return}
+            Err(err) => {util::thread_freeze(c_err, err); return} // pause thread, wait for main to
+                                                                  // exit
         }
     }
 }
@@ -52,7 +58,7 @@ pub fn write_raw_loop(mut cmd_out: ChildStdout, buff_size: usize, media_type: ut
     loop {
         let media = match read_raw(&mut cmd_out, buff_size, media_type) {
             Ok(x) => x,
-            Err(err) => {drop(c_out); thread::park(); return}
+            Err(err) => {drop(c_out); thread::park(); return} // drop to signal EOF to encoder
         };
         match c_out.send(media) {
             Ok(_) => (),

src/decode/codecs/video.rs

@@ -30,9 +30,12 @@ impl Decoder for H264Decoder {
 }
 
 pub fn new_h264(metadata: Arc<util::Metadata>) -> Result<H264Decoder, Box<dyn Error>> {
+    // ffmpeg pipe input output, H264 -> raw YUV420P sequence
     let cmd = Command::new("ffmpeg")
         .args(["-y", "-hide_banner", "-loglevel", "error" , "-i", "-", "-c:v", "rawvideo", "-pix_fmt", "yuv420p", "-f", "rawvideo", "-"])
         .stdin(Stdio::piped()).stdout(Stdio::piped()).spawn()?;
-    let bytes_per_sample = metadata.video.width * metadata.video.height * 3 / 2;
+    let bytes_per_sample = metadata.video.width * metadata.video.height * 3 / 2; // size of single
+                                                                                 // yuv is
+                                                                                 // 1.5*num_pixels
     return Ok(H264Decoder {cmd: cmd, raw_buff_size: bytes_per_sample as usize, raw_sample_type: util::RawMediaType::YUV420P});
 }

src/decode/mod.rs

@@ -22,7 +22,7 @@ pub fn spawn(
     let (raw_v_in, raw_v_out) = mpsc::channel();
     let (raw_a_in, raw_a_out) = mpsc::channel();
     let (err_in_v, err_out) = mpsc::channel();
-    let err_in_a = err_in_v.clone();
+    let err_in_a = err_in_v.clone(); // double for 2 threads
     let (v_decoder, a_decoder) = cmds::spawn(metadata.clone())?;
     thread::spawn(move || {
         cmds::handle_decoder(v_decoder, v, raw_v_in, err_in_v);

src/demux/flv.rs

@@ -30,6 +30,8 @@ pub struct FLVReader {
 
 impl FLVReader {
     fn check_signature(&mut self) -> Result<(), Box<dyn Error>> {
+        // check for "LV" for FLV header
+        // "F" already used in spawning, header[..4] always bytes "F" "L" "V" 0x1
         let mut sig_bytes_rem = [0u8; 3];
         self.stdin.read_exact(&mut sig_bytes_rem)?;
         if String::from_utf8(sig_bytes_rem[..2].to_vec())? != "LV" || sig_bytes_rem[2] != 1 {
@@ -39,6 +41,7 @@ impl FLVReader {
     }
 
     fn skip_init_header(&mut self) -> Result<(), Box<dyn Error>> {
+        // skip rest of header. Header is (FLV1 + 1byte + 4byte offset + 4byte reserved)
         let mut rest_of_header = [0u8; 5];
         self.stdin.read_exact(&mut rest_of_header)?;
         let head_offset = u32::from_be_bytes(rest_of_header[1..].try_into()?) as usize - 9 + 4;
@@ -48,13 +51,15 @@ impl FLVReader {
     }
 
     fn read_packet(&mut self) -> Result<(FLVTagType, Vec<u8>), Box<dyn Error + Send + Sync>> {
+        // FLV packet header always 11 bytes
         let mut tag_head = [0u8; 11];
         match self.stdin.read_exact(&mut tag_head) {
             Ok(_) => (),
-            Err(err) if err.kind() == io::ErrorKind::UnexpectedEof => return Err(Box::new(util::DemuxerError::EOF)),
+            Err(err) if err.kind() == io::ErrorKind::UnexpectedEof => return Err(Box::new(util::DemuxerError::EOF)), // assumes EOF while reading header means 0 bytes were read, not just less than len
             Err(err) => return Err(Box::new(err))
         };
         let tag_type = FLVTagType::try_from(tag_head[0])?;
+        // len is u24 not u32, u24 does not exist
         let tag_data_len = (u32::from_be_bytes(tag_head[..4].try_into()?) & 0xffffff) as usize;
         let mut packet_data = vec![0u8; tag_data_len];
         self.stdin.read_exact(packet_data.as_mut_slice())?;
@@ -85,6 +90,7 @@ impl input::FileReader for FLVReader {
     fn read_nalu(&mut self, metadata: &util::Metadata) -> Result<util::NALUPacket, Box<dyn Error + Send + Sync>> {
         let (packet_type, mut data) = self.read_packet()?;
         return match packet_type {
+            // add headers to raw bytestreams as needed
             FLVTagType::Audio => Ok(util::NALUPacket { 
                 packet_type: util::NALUPacketType::Audio(*metadata.audio.codec.as_ref().unwrap()),
                 packet_data: nalu::prepend_a(data, &metadata),
@@ -106,8 +112,10 @@ pub fn new_reader(stdin: io::Stdin) -> Result<FLVReader, Box<dyn Error>> {
 
 fn process_metadata(mut data: Vec<u8>) -> Result<util::Metadata, Box<dyn Error>> {
     let mut metadata = util::Metadata { ..Default::default() };
-    data.drain(..13);
+    data.drain(..13); // skip until ECMA array, hacky, but seems fixed length and I'm not
+                      // implementing a proper amf parser for 1 single tag that seems to be fixed length offset
     let ecma_sync_byte = data.drain(..1).next().unwrap();
+    // AMF ECMA array object marker
     if ecma_sync_byte != 8 {
         return Err(Box::new(util::DemuxerError::FLVMetadataSyncFail));
     }
@@ -115,8 +123,12 @@ fn process_metadata(mut data: Vec<u8>) -> Result<util::Metadata, Box<dyn Error>>
     for _ in 0..arr_len {
         let key = String::fetch_amf_val(&mut data);
         let amf_marker = u8::fetch_amf_val(&mut data);
-        if !handle_relevant_keys(key, &mut data, &mut metadata)? {
+        if !handle_relevant_keys(key, &mut data, &mut metadata)? { // most are completely useless
+                                                                   // or unused (levels), if they
+                                                                   // are, get the value
             match amf_marker {
+                // added functions to base types, see below.
+                // would try generics, but restricting types is weird
                 0 => {let _ = f64::fetch_amf_val(&mut data);},
                 1 => {let _ = bool::fetch_amf_val(&mut data);},
                 2 => {let _ = String::fetch_amf_val(&mut data);},
@@ -124,11 +136,13 @@ fn process_metadata(mut data: Vec<u8>) -> Result<util::Metadata, Box<dyn Error>>
             }
         }
     }
+    // check if all needed values are set
     return if metadata.is_valid() {Ok(metadata)} else {Err(Box::new(util::DemuxerError::MetadataValNotSet))};
 }
 
 fn handle_relevant_keys(key: String, data: &mut Vec<u8>, metadata: &mut util::Metadata) -> Result<bool, Box<dyn Error>> {
     match key.as_str() {
+        // fetches relevant values, should try to use above instead, but codecs complicate things
         "width" => {metadata.video.width = f64::fetch_amf_val(data) as u32; Ok(true)},
         "height" => {metadata.video.height = f64::fetch_amf_val(data) as u32; Ok(true)},
         "framerate" => {metadata.video.framerate = f64::fetch_amf_val(data) as f32; Ok(true)},

src/demux/input.rs

@@ -15,18 +15,20 @@ pub trait FileReader {
             let nalu = match self.read_nalu(&metadata) {
                 Ok(x) => x,
                 Err(err) => {
+                    // pause loop on EOF
                     if let Some(e) = err.downcast_ref::<util::DemuxerError>() {
                         match e {
                             util::DemuxerError::EOF => {
+                                // drop to trigger RecvError on decode module to end
                                 drop(v_in);
                                 drop(a_in);
-                                thread::park();
+                                thread::park(); // prevent dropping err_out to keep main running
                                 return
                             },
                             _ => ()
                         }
                     };
-                    util::thread_freeze(err_in, err);
+                    util::thread_freeze(err_in, err); // pause thread, trigger main to exit
                     return
                 }
             };
@@ -50,7 +52,7 @@ pub trait FileReader {
 
 pub fn new_reader() -> Result<impl FileReader, Box<dyn Error>> {
     let mut stdin_hndl = io::stdin();
-    let mut byte1 = [0u8; 1];
+    let mut byte1 = [0u8; 1]; // sync byte to determine filetype, limited checking capability
     stdin_hndl.read_exact(&mut byte1)?;
     match &byte1[0] {
         0x46 => flv::new_reader(stdin_hndl),

src/demux/mod.rs

@@ -1,6 +1,6 @@
 mod input;
 mod flv;
-mod nalu_flv;
+mod nalu_flv; // probably should organize into an flv submodule instead, but eh
 
 use std::sync::mpsc;
 use std::error::Error;
@@ -20,7 +20,7 @@ pub fn spawn() -> Result<
     Box<dyn Error>
     > {
     let mut reader = input::new_reader()?;
-    let metadata = Arc::new(reader.init()?);
+    let metadata = Arc::new(reader.init()?); // arc to share across modules
     let (v_in, v_out) = mpsc::channel();
     let (a_in, a_out) = mpsc::channel();
     let (err_in, err_out) = mpsc::channel();

src/demux/nalu_flv.rs

@@ -29,25 +29,28 @@ fn parse_avcc(mut data: Vec<u8>) -> (Vec<u8>, Vec<u8>) {
 }
 
 fn preprocess_h264(mut data: Vec<u8>) -> Vec<u8> {
-    let mut nalu = vec![0u8, 0u8, 0u8, 1u8];
+    let mut nalu = vec![0u8, 0u8, 0u8, 1u8]; // base nalu delimiter for H264
     match data[1] {
         0 => {
-            data.drain(..5);
+            // sequence header contains avcC as in ISOBMF binding,
+            // contains sps and pps needed for bytestream
+            // must be segmented for NALU format
+            data.drain(..5); // composition time info, etc, see FLV spec
             let (mut sps, mut pps) = parse_avcc(data);
             nalu.append(&mut sps);
             nalu.append(&mut vec![0u8, 0u8, 0u8, 1u8]);
             nalu.append(&mut pps);
             return nalu;
         },
-        2 => {return vec![0u8; 0];},
+        2 => {return vec![0u8; 0];}, // end seq, return null
         1 => {
             data.drain(..5);
-            loop {
+            loop { // may be multiple NALU packets per tag
                 let mut buff = [0u8; 4];
                 buff.copy_from_slice(data.drain(..4).as_slice());
                 let nalu_len = u32::from_be_bytes(buff) as usize;
                 nalu.extend_from_slice(data.drain(..nalu_len).as_slice());
-                if data.len() <= 4 {return nalu}
+                if data.len() <= 4 {return nalu} // at end of packet
                 nalu.append(&mut vec![0u8, 0u8, 0u8, 1u8]);
             }
         },
@@ -56,6 +59,7 @@ fn preprocess_h264(mut data: Vec<u8>) -> Vec<u8> {
 }
 
 fn make_adts_head(metadata: &util::Metadata, data_len: usize) -> Vec<u8> {
+    // see multimedia wiki for details
     let aot_idx = 1u8;
     let frame_len = (data_len + 7) as u16;
     let samplerate_idx: u8 = match metadata.audio.samplerate {
@@ -75,7 +79,8 @@ fn make_adts_head(metadata: &util::Metadata, data_len: usize) -> Vec<u8> {
         _ => {panic!("invalid samplerate")}
     };
     let chan_conf_idx = metadata.audio.channels;
-    let mut head = vec![0xffu8, 0xf1u8, 0u8, 0u8, 0u8, 0u8, 0xfcu8];
+    let mut head = vec![0xffu8, 0xf1u8, 0u8, 0u8, 0u8, 0u8, 0xfcu8]; // sync bytes and guaranteed
+                                                                     // value set
     head[2] = (aot_idx << 6) | (samplerate_idx << 2) | (chan_conf_idx >> 2);
     head[3] = ((chan_conf_idx & 0x3) << 6) | ((frame_len >> 11) as u8);
     head[4] = ((frame_len >> 3) & 0xff) as u8;
@@ -86,6 +91,8 @@ fn make_adts_head(metadata: &util::Metadata, data_len: usize) -> Vec<u8> {
 fn preprocess_aac(mut data: Vec<u8>, metadata: &util::Metadata) -> Vec<u8> {
     match data[1] {
         0 => {
+            // bytestream needs no codec config, all information already in metadata, also would
+            // not be persistent across packets
             return vec![0u8; 0];
         },
         1 => {

src/encode/cmds.rs

@@ -6,6 +6,7 @@ use crate::util;
 use crate::encode::codecs::Encoder;
 use crate::encode::codecs;
 
+// spawn encoder for a given output encoding
 pub fn spawn(metadata: Arc<util::Metadata>, v_target: util::VideoCodec, a_target: util::AudioCodec) -> Result<(impl Encoder + Send, impl Encoder + Send), Box<dyn Error>> {
     let v = match v_target {
         util::VideoCodec::AV1 => codecs::video::new_av1(metadata.clone())?,

src/encode/codecs/audio.rs

@@ -18,19 +18,21 @@ impl Encoder for OpusEncoder {
     }
 
     fn preprocess_stream(&mut self) -> Result<(), Box<dyn Error + Send + Sync>> {
+        // opus outputs Ogg format, can be parsed with the same parser as the rest
         return Ok(());
     }
 
     fn read_nalu(&mut self) -> Result<util::NALUPacket, Box<dyn Error + Send + Sync>> {
         let mut stdout = self.cmd.stdout.as_mut().unwrap();
-        let mut buff = [0u8; 27];
+        let mut buff = [0u8; 27]; // each packet has a 27 byte header, mostly irrelevant
         match stdout.read_exact(&mut buff) {
             Ok(_) => (),
-            Err(err) if err.kind() == io::ErrorKind::UnexpectedEof => return Err(Box::new(util::EncoderError::EOF)),
+            Err(err) if err.kind() == io::ErrorKind::UnexpectedEof => return Err(Box::new(util::EncoderError::EOF)), // assume EOF at header means EOF proper
             Err(err) => return Err(Box::new(err))
         };
         let num_segments = buff[buff.len() - 1] as usize;
-        let mut segment_table_buff = vec![0u8; num_segments];
+        let mut segment_table_buff = vec![0u8; num_segments]; // dictates actual size of data as
+                                                              // raw sum of u8
         stdout.read_exact(&mut segment_table_buff)?;
         let mut page_size:usize = 0;
         for i in segment_table_buff {
@@ -45,6 +47,7 @@ impl Encoder for OpusEncoder {
 pub fn new_opus(metadata: Arc<util::Metadata>) -> Result<OpusEncoder, Box<dyn Error>> {
     let channels = metadata.audio.channels.to_string();
     let samplerate = metadata.audio.samplerate.to_string();
+    // opus enc for PCM LE 16 -> Opus
     let cmd = Command::new("opusenc")
         .args([
             "--quiet",
@@ -52,7 +55,7 @@ pub fn new_opus(metadata: Arc<util::Metadata>) -> Result<OpusEncoder, Box<dyn Er
             "--raw-bits", "16",
             "--raw-rate", samplerate.as_str(),
             "--raw-chan", channels.as_str(),
-            "--max-delay", "1",
+            "--max-delay", "1", // 0 works worse than 1 somehow
             "-", "-"
         ]).stdin(Stdio::piped()).stdout(Stdio::piped()).spawn()?;
     return Ok(OpusEncoder {cmd: cmd});

src/encode/codecs/mod.rs

@@ -12,8 +12,13 @@ use crate::util;
 pub trait Encoder {
     fn stdin(&mut self) -> ChildStdin;
     
+    // read from encoder
     fn read_nalu(&mut self) -> Result<util::NALUPacket, Box<dyn Error + Send + Sync>>;
 
+    // for specific encoder peculiarities
+    // svtav1 gives DKIF format, which has its own extra header which breaks just parsing as is
+    // opus outputs Ogg which needs full and header follows the same format as the rest for packets
+    // use as needed
     fn preprocess_stream(&mut self) -> Result<(), Box<dyn Error + Send + Sync>>;
 
     fn write_nalu_loop(&mut self, c_out: mpsc::Sender<util::NALUPacket>, c_err: mpsc::Sender<Box<dyn Error + Send + Sync>>) {
@@ -24,7 +29,9 @@ pub trait Encoder {
         loop {
             let nalu = match self.read_nalu() {
                 Ok(x) => x,
-                Err(err) => {drop(c_out); thread::park(); return}
+                Err(err) => {drop(c_out); thread::park(); return} // drop c_out to signal EOF to
+                                                                  // muxer, park to keep c_err
+                                                                  // allocated
             };
             match c_out.send(nalu) {
                 Ok(_) => (),
@@ -34,6 +41,7 @@ pub trait Encoder {
     }
 }
 
+// write to encoder
 fn write_raw(cmd_in: &mut ChildStdin, media: util::RawMedia) -> Result<(), Box<dyn Error + Send + Sync>> {
     cmd_in.write_all(media.sample.as_slice())?;
     Ok(())
@@ -43,11 +51,15 @@ pub fn read_raw_loop(mut cmd_in: ChildStdin, c_in: mpsc::Receiver<util::RawMedia
     loop {
         let media = match c_in.recv() {
             Ok(x) => x,
-            Err(err) => {drop(cmd_in); thread::park(); return}
+            Err(err) => {drop(cmd_in); thread::park(); return} // drop stdin to signal EOF, which
+                                                               // lets encoder close stdout as
+                                                               // needed, park to keep c_err
+                                                               // allocated
         };
         match write_raw(&mut cmd_in, media) {
             Ok(_) => (),
-            Err(err) => {util::thread_freeze(c_err, err); return}
+            Err(err) => {util::thread_freeze(c_err, err); return} // park thread, wait for main to
+                                                                  // exit
         }
     }
 }

src/encode/codecs/video.rs

@@ -17,7 +17,9 @@ impl Encoder for AV1Encoder {
     }
 
     fn preprocess_stream(&mut self) -> Result<(), Box<dyn Error + Send + Sync>> {
+        // SVTAV1 outputs Duck IVF framing, check specs if needed
         let mut stdout = self.cmd.stdout.as_mut().unwrap();
+        // remove dkif header
         let mut buff = [0u8; 8];
         stdout.read_exact(&mut buff)?;
         let head_len = u16::from_le_bytes(buff[6..].try_into().unwrap()) as usize;
@@ -28,16 +30,18 @@ impl Encoder for AV1Encoder {
 
     fn read_nalu(&mut self) -> Result<util::NALUPacket, Box<dyn Error + Send + Sync>> {
         let mut stdout = self.cmd.stdout.as_mut().unwrap();
-        let mut buff = [0u8; 12];
+        let mut buff = [0u8; 12]; // frame always 12 byte header
         match stdout.read_exact(&mut buff) {
             Ok(_) => (),
-            Err(err) if err.kind() == io::ErrorKind::UnexpectedEof => return Err(Box::new(util::EncoderError::EOF)),
+            Err(err) if err.kind() == io::ErrorKind::UnexpectedEof => return Err(Box::new(util::EncoderError::EOF)), // assume eof if header read fails
             Err(err) => return Err(Box::new(err))
         }
-        let nalu_len = u32::from_le_bytes(buff[..4].try_into().unwrap()) as usize;
+        let nalu_len = u32::from_le_bytes(buff[..4].try_into().unwrap()) as usize; // actual sample
+                                                                                   // size in frame
+                                                                                   // header
         let mut data = vec![0u8; nalu_len];
         stdout.read_exact(data.as_mut_slice())?;
-        data.drain(..2);
+        data.drain(..2); // skip temporal delimiter packet (2 bytes, always first of each dkif frame)
         return Ok(util::NALUPacket {packet_type: util::NALUPacketType::Video(util::VideoCodec::AV1), packet_data: data});
     }
 }
@@ -46,15 +50,16 @@ pub fn new_av1(metadata: Arc<util::Metadata>) -> Result<AV1Encoder, Box<dyn Erro
     let width = metadata.video.width.to_string();
     let height = metadata.video.height.to_string();
     let fps_num = ((metadata.video.framerate * 1000.0) as u32).to_string();
+    // SVTAV1 for YUV420 -> AV1, piped input output
     let cmd = Command::new("SvtAv1EncApp")
         .args([
-            "--errlog", "/dev/null",
+            "--errlog", "/dev/null", // dump errors
             "--progress", "0",
             "-w", width.as_str(),
             "-h", height.as_str(),
             "--fps-num", fps_num.as_str(),
-            "--preset", "12",
+            "--preset", "12", // super fast
-            "--keyint", "30",
+            "--keyint", "30", // keyframe every 30 frames
             "-i", "-",
             "-b", "-"
         ]).stdin(Stdio::piped()).stdout(Stdio::piped()).spawn()?;

src/encode/mod.rs

@@ -24,7 +24,7 @@ pub fn spawn(
     let (v_in, v_out) = mpsc::channel();
     let (a_in, a_out) = mpsc::channel();
     let (err_in_v, err_out) = mpsc::channel();
-    let err_in_a = err_in_v.clone();
+    let err_in_a = err_in_v.clone(); // double for each thread
     let (v_encoder, a_encoder) = cmds::spawn(metadata, v_target, a_target)?;
     thread::spawn(move || {
         cmds::handle_encoder(v_encoder, v, v_in, err_in_v);

src/main.rs

@@ -9,21 +9,28 @@ use std::sync::mpsc;
 use std::thread;
 use std::time::Duration;
 
-fn init(args: util::HLSArgs) -> Result<[mpsc::Receiver<Box<dyn std::error::Error + Send + Sync>>; 4], Box<dyn std::error::Error>>{
+// spawns threads for each subtask, linking input/output channels
+// returns an array of error receivers to exit if needed
+// passes input metadata around for video and audio metadata, makes scaling and resampling
+// impossible
+fn init(args: util::HLSArgs) -> Result<[mpsc::Receiver<Box<dyn std::error::Error + Send + Sync>>; 4], Box<dyn std::error::Error>> {
     let (v_out, a_out, metadata, demux_err_recv) = demux::spawn()?;
     let (raw_v_out, raw_a_out, decode_err_recv) = decode::spawn(v_out, a_out, metadata.clone())?;
+    // output codecs hardcoded, probably want to pass in via cmd args instead
     let (enc_v_out, enc_a_out, encode_err_recv) = encode::spawn(raw_v_out, raw_a_out, metadata.clone(), util::VideoCodec::AV1, util::AudioCodec::OPUS)?;
     let muxer_err_recv = muxer::spawn(enc_v_out, enc_a_out, metadata.clone(), args)?;
     return Ok([demux_err_recv, decode_err_recv, encode_err_recv, muxer_err_recv]);
 }
 
+// post init loop. Modules are initialized without error, loop and check for errors
 fn process(error_handles: [mpsc::Receiver<Box<dyn std::error::Error + Send + Sync>>; 4]) -> Result<(), Box<dyn std::error::Error>> {
-    let (mut v_eof, mut a_eof) = (false, false);
+    let (mut v_eof, mut a_eof) = (false, false); // proper EOF handling
     loop {
-        if v_eof && a_eof {return Ok(())}
+        if v_eof && a_eof {return Ok(())} // if both video and audio streams have ended
         for i in 0..4 {
             match error_handles[i].try_recv() {
                 Ok(err) => {
+                    // check if EOF error found.
                     if let Some(eof_error) = err.downcast_ref::<util::MuxerError>() {
                         match eof_error {
                             util::MuxerError::VideoEOF => {v_eof = true;},
@@ -34,17 +41,22 @@ fn process(error_handles: [mpsc::Receiver<Box<dyn std::error::Error + Send + Syn
                         return Err(err)
                     }
                 },
-                Err(mpsc::TryRecvError::Empty) => (),
+                Err(mpsc::TryRecvError::Empty) => (), // do nothing since nothing was sent and
+                                                      // thread still active
                 Err(err) => return Err(Box::new(util::ThreadError(i))),
             }
         }
-        thread::sleep(Duration::from_millis(100));
+        thread::sleep(Duration::from_millis(100)); // sleep so isn't running constantly for no
+                                                   // reason
     }
 }
 
+
+// gets args
+// bad, replace with clap impl if meaning to actually use
 fn parse_args() -> util::HLSArgs {
     let mut args = std::env::args();
-    args.next();
+    args.next(); // skip prog name
     util::HLSArgs {
         segment_time: args.next().expect("no time interval").parse().expect("not int"),
         segment_prepend: args.next().expect("no prepend"),

src/muxer/hls/handler.rs

@@ -26,20 +26,22 @@ impl HLSHandler {
             match self.muxer.get_segment(self.curr_segment_idx, self.args.segment_time) {
                 None => (),
                 Some(segment) => {
-                    let del_list = self.new_segment(segment);
+                    let del_list = self.new_segment(segment); // making a new segment should push
+                                                              // out old segments
                     self.delete_files(del_list);
                     self.dump_playlist();
                     self.curr_segment_idx += 1;
                 }
             }
-            thread::sleep(time::Duration::from_millis(100));
+            thread::sleep(time::Duration::from_millis(100)); // don't need to have it constantly
+                                                             // running,
         }
     }
 
     fn new_segment(&mut self, segment: segments::Segment) -> Vec<String> {
-        segment.dump();
+        segment.dump(); // write out the segment,
-        self.curr_segments.push(segment.filename);
+        self.curr_segments.push(segment.filename); // add its filename to the curr playlist,
-        let to_drain = if self.curr_segments.len() > self.args.max_segments {self.curr_segments.len() - self.args.max_segments} else {0};
+        let to_drain = if self.curr_segments.len() > self.args.max_segments {self.curr_segments.len() - self.args.max_segments} else {0}; // and remove segement filenames that are old
         self.curr_segments.drain(..to_drain).collect()
     }
 
@@ -47,18 +49,23 @@ impl HLSHandler {
     fn delete_files(&mut self, mut del_list: Vec<String>) {
         for filename in &del_list {
             _ = fs::remove_file(filename);
-            self.curr_media_seq_idx += 1;
+            self.curr_media_seq_idx += 1; // media sequence must increment per deletion as per HLS
+                                          // spec
         }
     }
 
     fn dump_playlist(&self) {
         let mut segment_listing = String::new();
         for segment_filename in &self.curr_segments {
+            // each segment has its duration and access URI, should also have Datetime, but neither
+            // really needed nor "simple" with std rust, would need chrono or time or be ready for
+            // headaches
             segment_listing += format!("\
             #EXTINF:{},\n\
             {}\n\
             ", self.args.segment_time, (self.args.segment_prepend.clone() + segment_filename)).as_str();
         }
+        // full playlist string, see HLS spec for details
         let playlist_string = format!("\
         #EXTM3U\n\
         #EXT-X-VERSION:7\n\

src/muxer/hls/mp4/atoms.rs

@@ -1,3 +1,8 @@
+// cursed abomination, not well thought out, but works fine, rust also complicates inheritance
+// every necessary MP4 atom to create readable files,
+// lookup the corresponding item in the ISO doc or the quicktime spec (for everything not under
+// moof), because I am not doing all of that here.
+
 use std::sync::Arc;
 use std::io::Write;
 use std::fs::File;
@@ -921,6 +926,7 @@ pub fn construct_moov(stsd_v: STSD, stsd_a: STSD, metadata: &Arc<util::Metadata>
     }
 }
 
+// video will always be track 1, audio in trak 2
 fn new_trak(stsd: STSD, metadata: &Arc<util::Metadata>) -> TRAK {
     let mut tkhd = TKHD {..Default::default() };
     match stsd.entry {
@@ -1192,6 +1198,11 @@ impl MP4Atom for MDAT {
 }
 
 pub fn new_moof(v_samples: &Vec<samples::Sample>, default_dur_v: u32, a_samples: &Vec<samples::Sample>, default_dur_a: u32, mdat_v_offset: usize, mdat_a_offset: usize, moof_idx: usize) -> MOOF {
+    // hacky fix, since sticking to a standard format and defaults for segments, only trun is
+    // variable which has a predictable size regardless, moof offset + v and a trun sample table
+    // len and mdat header offset, will break using version 1 atoms for time,
+    // alternative is to somehow record idx for base offset (which breaks MP4atoms impl) to modify
+    // later, or calc full length properly, also complicated
     let mdat_data_start = 152 + v_samples.len() * 8 + a_samples.len() * 8 + 8;
     MOOF {
         mfhd: MFHD { seq_num: moof_idx as u32, ..Default::default() },
@@ -1241,6 +1252,7 @@ fn make_sample_table(samples: &Vec<samples::Sample>) -> Vec<SampleData> {
     return table;
 }
 
+// takes content, applies MP4 atom encapsulation
 fn make_box(mut content: Vec<u8>, box_name: [u8; 4]) -> Vec<u8> {
     let mut head = vec![0u8; 8];
     head.splice(..4, ((content.len() + 8) as u32).to_be_bytes());

src/muxer/hls/mp4/mod.rs

@@ -8,6 +8,7 @@ use std::error::Error;
 use crate::util;
 
 pub struct MP4Muxer {
+    // option to allow being taken by threads
     v: Option<mpsc::Receiver<util::NALUPacket>>,
     pub v_samples: Arc<samples::SampleQueue>,
     a: Option<mpsc::Receiver<util::NALUPacket>>,
@@ -22,15 +23,22 @@ pub fn new_muxer(v: mpsc::Receiver<util::NALUPacket>, a: mpsc::Receiver<util::NA
         a: Some(a),
         metadata: metadata.clone(),
         err_in: err_in,
+        // Arc<Mutex<Vec>> for multithread write access
         v_samples: Arc::new(samples::SampleQueue {
             queue: Mutex::new(Vec::new()),
-            default_duration: 1000,
+            default_duration: 1000, // timescale as fps * 1000, each sample then always 1000
+                                    // regardless of fps
             samples_per_sec:  metadata.video.framerate as usize,
         }),
         a_samples: Arc::new(samples::SampleQueue {
             queue: Mutex::new(Vec::new()),
-            default_duration: metadata.audio.samplerate * 20 / 1000,
+            default_duration: metadata.audio.samplerate * 20 / 1000, // timescale set as
-            samples_per_sec: 50,
+                                                                     // samplerate, duration per
+                                                                     // sample is sample duration
+                                                                     // (20ms packet) * samples per
+                                                                     // time (samplerate)
+            samples_per_sec: 50, // opus default is 20ms packets (1000/20 = 50), would need to change this if
+                                 // changing that
         }),
     };
     muxer.gen_init()?;

src/muxer/hls/mp4/mp4muxer.rs

@@ -11,12 +11,17 @@ impl mp4::MP4Muxer {
     pub fn gen_init(&mut self) -> Result<(), Box<dyn Error>> {
         let stsd_v = self.handle_v_cc()?;
         let stsd_a = self.handle_a_cc()?;
+        // only need moov for codec declarations, ftyp is uneeded apparently
         let init_tree = mp4::atoms::construct_moov(stsd_v, stsd_a, &self.metadata);
-        mp4::atoms::dump_init_tree(init_tree)?;
+        mp4::atoms::dump_init_tree(init_tree)?; // write out moov in init.mp4 segment
         Ok(())
     }
 
     fn handle_v_cc(&mut self) -> Result<mp4::atoms::STSD, Box<dyn Error>> {
+        // handles getting stsd per sample, parsing codec config mostly
+        // and peculiarities per codec
+        // AV1 has the first nalu as is in the samples
+        // also contains info for codec config
         let v_cc = self.v.as_ref().expect("must be owned at init").recv()?;
         return match v_cc.packet_type {
             util::NALUPacketType::Video(util::VideoCodec::AV1) => {
@@ -28,6 +33,10 @@ impl mp4::MP4Muxer {
     }
 
     fn handle_a_cc(&mut self) -> Result<mp4::atoms::STSD, Box<dyn Error>> {
+        // handles getting stsd per sample, parsing codec config mostly
+        // and peculiarities per codec
+        // Ogg (Opus) first packet has codec config info, not needed in samples
+        // Second packet has no discernable use for ISOBMF? Also not needed in samples
         let a_cc = self.a.as_ref().expect("must be owned at init").recv()?;
         return match a_cc.packet_type {
             util::NALUPacketType::Audio(util::AudioCodec::OPUS) => {
@@ -48,8 +57,15 @@ impl mp4::MP4Muxer {
             let mut i = 1;
             loop {
                 match v.recv() {
+                    // hacky fix for video keyframe sample flags
+                    // set at 30 frames per keyframe, would need some way to send the same value to
+                    // the encoder as here or attempt to parse the actual OBU (even the header
+                    // seems cursed, just use a lib instead)
+                    // no clue how those flags are parsed, but they work (0x02 is keyframe, 0x0101
+                    // is interframe)
                     Ok(x) => {v_queue.push(x.packet_data, if i % 30 == 0 {0x02000000} else {0x01010000});},
                     Err(_) => {
+                        // send EOF to main for proper shutdown
                         util::thread_freeze(err_in1, Box::new(util::MuxerError::VideoEOF));
                         return
                     }
@@ -61,8 +77,11 @@ impl mp4::MP4Muxer {
         thread::spawn(move || {
             loop {
                 match a.recv() {
+                    // audio should be all keyframes, should use the tfhd default var, but
+                    // more work to decouple video and audio impls
                     Ok(x) => {a_queue.push(x.packet_data, 0x02000000);},
                     Err(_) => {
+                        // send EOF for proper shutdown
                         util::thread_freeze(err_in2, Box::new(util::MuxerError::AudioEOF));
                         return
                     }
@@ -72,6 +91,9 @@ impl mp4::MP4Muxer {
     }
 
     pub fn get_segment(&mut self, idx: usize, time: usize) -> Option<segments::Segment> {
+        // if sample queues are long enough to extract a segment, do so, otherwise return None
+        // probably should not be an option, instead loop here until ready to allow flushing at
+        // exit
         if self.v_samples.segment_ready(time) && self.a_samples.segment_ready(time) {
             return Some(segments::Segment {
                 filename: idx.to_string() + ".m4s",
@@ -100,7 +122,7 @@ fn get_av1_stsd(mut sample: Vec<u8>, metadata: &Arc<util::Metadata>) -> mp4::ato
         dref_idx: 1,
         width: metadata.video.width as u16,
         height: metadata.video.height as u16,
-        resolution: (72u64 << 48) + (72u64 << 16),
+        resolution: (72u64 << 48) + (72u64 << 16), // 72 dpi, fixed point numbers (72.00 + 72.00)
         sample_per_frame: 1,
         encoder_name: String::from("libsvtav1"),
         pixel_depth: 24,
@@ -115,6 +137,7 @@ fn get_av1_stsd(mut sample: Vec<u8>, metadata: &Arc<util::Metadata>) -> mp4::ato
 }
 
 fn get_opus_stsd(sample: Vec<u8>, metadata: &Arc<util::Metadata>) -> mp4::atoms::STSD {
+    // see opus encapsulation in ISOBMF for details
     let mut opus_binding = vec![0u8; 11];
     opus_binding[1] = metadata.audio.channels;
     let pre_skip = u16::from_le_bytes(sample[10..12].try_into().unwrap());
@@ -132,7 +155,7 @@ fn get_opus_stsd(sample: Vec<u8>, metadata: &Arc<util::Metadata>) -> mp4::atoms:
         dref_idx: 1,
         channels: metadata.audio.channels as u16,
         sample_size: 16,
-        sample_rate: metadata.audio.samplerate << 16,
+        sample_rate: metadata.audio.samplerate << 16, // fixed point (u16 int + u16 decimals)
         codec_config: mp4::atoms::CodecConfig { atom_name: *b"dOps", data: opus_binding}
     };
     return mp4::atoms::STSD {

src/muxer/hls/mp4/samples.rs

@@ -2,6 +2,8 @@ use std::sync::{Arc, Mutex};
 
 use crate::muxer::hls::segments;
 
+// forces a common duration, no composition time offset
+// flags declared per sample as well as size
 pub struct Sample {
     pub data: Vec<u8>,
     pub size: u32,

src/muxer/hls/segments.rs

@@ -10,14 +10,16 @@ pub struct Segment {
     pub filename: String,
     pub idx: usize,
     pub segment_video: Vec<samples::Sample>,
-    pub sample_duration_v: u32,
+    pub sample_duration_v: u32, // default interval per sample at designated timescale (same for
+                                // audio instead below)
     pub segment_audio: Vec<samples::Sample>,
     pub sample_duration_a: u32,
 }
 
 impl Segment {
     pub fn dump(&self) {
-        let mdat = self.new_mdat();
+        let mdat = self.new_mdat(); // sample full byte length needed for moof generation
+        // increment idx (0-indexed) for moofs (1-indexed)
         let moof = atoms::new_moof(&self.segment_video, self.sample_duration_v, &self.segment_audio, self.sample_duration_a, 0, mdat.v_samples.len(), self.idx + 1);
         let mut segment_bytes = moof.marshall();
         segment_bytes.append(&mut mdat.marshall());

src/util/mod.rs

@@ -1,3 +1,5 @@
+// general use structs, functions and errors go here
+
 use std::error::Error;
 use std::fmt;
 use std::thread;
@@ -222,11 +224,15 @@ impl fmt::Display for MuxerError {
 }
 // funcs
 
+// parks a thread and sends an error over the param channel
+// used to pause threads keeping channels open, so that main can receive the actual error and then
+// exit, instead of a "RecvError"
 pub fn thread_freeze(err_sender: mpsc::Sender<Box<dyn Error + Send + Sync>>, err: Box<dyn Error + Send + Sync>) {
     err_sender.send(err).unwrap();
     thread::park();
 }
 
+// should probably make this a macro instead, eh
 pub fn blank_vec(n: usize) -> Vec<u8> {
     return vec![0u8; n];
 }