84 lines
3.7 KiB
Zig
84 lines
3.7 KiB
Zig
const std = @import("std");
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const util = @import("util.zig");
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const threads = @import("threads.zig");
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const output = @import("output.zig");
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// helper func, computes the appropriate coords for luminance
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// [macro_block][macro_block][intra_macro_block]
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inline fn lum_idxs(i: usize, j: usize) struct { usize, usize, usize } {
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return .{
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i / 2,
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j / 2,
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2 * (i % 2) + (j % 2),
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};
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}
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// either 2 separate funcs (see read_chrom) or multiple if statements, will be bad anyway
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// incrementally copies 8 byte sequences from the input buffer to the appropriate coords in the Y buffer
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// sends any completed blocks off to be processed for quantization as they fill
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fn read_lum(f: std.fs.File, source_buff: [][][4]util.Block, target_buff: [][][4]util.BlockQuantized, io_buff: []u8, queue: *util.JobQueue) !void {
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const block_h = source_buff.len;
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const block_w = source_buff[0].len;
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for (0..block_h * 2) |i| {
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if (io_buff.len != try f.readAll(io_buff)) return util.Errors.EOFError;
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var io_idx: usize = 0;
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for (0..8) |I| {
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for (0..block_w * 2) |j| {
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const idxs = lum_idxs(i, j);
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@memcpy(source_buff[idxs.@"0"][idxs.@"1"][idxs.@"2"][I * 8 .. (I + 1) * 8], io_buff[io_idx .. io_idx + 8]);
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io_idx += 8;
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if (I == 7) {
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try queue.prepend(util.Job{
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.source = &source_buff[idxs.@"0"][idxs.@"1"][idxs.@"2"],
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.target = &target_buff[idxs.@"0"][idxs.@"1"][idxs.@"2"],
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.is_lum = true,
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});
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}
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}
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}
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}
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}
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// either 2 separate funcs (see read_lum) or multiple if statements, will be bad anyway
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// incrementally copies 8 byte sequences from the input buffer to the appropriate coords in the U or V buffer
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// sends any completed blocks off to be processed for quantization as they fill
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fn read_chrom(f: std.fs.File, source_buff: [][]util.Block, target_buff: [][]util.BlockQuantized, io_buff: []u8, queue: *util.JobQueue) !void {
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const block_h = source_buff.len;
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const block_w = source_buff[0].len;
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for (0..block_h) |i| {
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if (io_buff.len != try f.readAll(io_buff)) return util.Errors.EOFError;
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var io_idx: usize = 0;
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for (0..8) |I| {
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for (0..block_w) |j| {
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@memcpy(source_buff[i][j][I * 8 .. (I + 1) * 8], io_buff[io_idx .. io_idx + 8]);
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io_idx += 8;
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if (I == 7) {
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try queue.prepend(util.Job{
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.source = &source_buff[i][j],
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.target = &target_buff[i][j],
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.is_lum = false,
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});
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}
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}
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}
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}
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}
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pub fn main_loop(f: std.fs.File, buffs: util.Buffers, thread_mgr: *threads.ThreadManager, alloc: std.mem.Allocator) !void {
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defer thread_mgr.quit();
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while (true) {
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// resets control atomic variables, resumes quantizers
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thread_mgr.unblock();
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try read_lum(f, buffs.Y, buffs.Y_quant, buffs.input_buff, thread_mgr.queue_wrp.queue);
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// U and V are downsampled, half len buffers
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try read_chrom(f, buffs.U, buffs.U_quant, buffs.input_buff[0 .. buffs.input_buff.len / 2], thread_mgr.queue_wrp.queue);
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try read_chrom(f, buffs.V, buffs.V_quant, buffs.input_buff[0 .. buffs.input_buff.len / 2], thread_mgr.queue_wrp.queue);
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// wait until all blocks have been processed
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while (thread_mgr.signals.processed.load(.Acquire) != buffs.num_blocks) : (std.time.sleep(1)) {}
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// sets the eof signal atomic variable, prevents quantizers from checking jobs when none can generate
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thread_mgr.eof();
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try output.generate_jpg(buffs, alloc);
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}
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}
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