From 792f490c44355c95e72d18010f7dc2c8c8449e59 Mon Sep 17 00:00:00 2001 From: Kostya Shishkov Date: Wed, 17 May 2023 18:27:39 +0200 Subject: [PATCH] flacdemux: improve frame bounds search --- nihav-llaudio/src/demuxers/flac.rs | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/nihav-llaudio/src/demuxers/flac.rs b/nihav-llaudio/src/demuxers/flac.rs index 055f4fd..215a1e9 100644 --- a/nihav-llaudio/src/demuxers/flac.rs +++ b/nihav-llaudio/src/demuxers/flac.rs @@ -21,6 +21,17 @@ struct FLACDemuxer<'a> { srate: u32, known_frames: Vec, build_index: bool, + frame_hdr: u32, +} + +fn common_header_word(mut val: u32) -> u32 { + val &= !0x1F000; // blocking strategy and block size + let ch_map = (val >> 4) & 0xF; + if matches!(ch_map, 0x1 | 0x8 | 0x9 | 0xA) { // stereo coding modes + val &= !0xF0; + val |= 0x10; + } + val } impl<'a> FLACDemuxer<'a> { @@ -37,6 +48,7 @@ impl<'a> FLACDemuxer<'a> { srate: 0, known_frames: Vec::new(), build_index: false, + frame_hdr: 0, } } fn read_frame(&mut self) -> DemuxerResult<(Vec, u64, u64)> { @@ -49,6 +61,9 @@ impl<'a> FLACDemuxer<'a> { buf.push(byte); crc = update_crc16(crc, byte); } + if self.frame_hdr == 0 { + self.frame_hdr = read_u32be(&buf).unwrap_or(0); + } let mut ref_crc = self.src.read_u16be()?; loop { let byte = self.src.read_byte()?; @@ -56,9 +71,9 @@ impl<'a> FLACDemuxer<'a> { buf.push(old_byte); ref_crc = (ref_crc << 8) | u16::from(byte); crc = update_crc16(crc, old_byte); - if buf.len() + 2 >= self.min_size && crc == ref_crc { - let ret = self.src.peek_u16be(); - if ret.is_err() || ((ret.unwrap_or(0) & 0xFFFE) == 0xFFF8) { + if buf.len() + 4 >= self.min_size && crc == ref_crc { + let ret = self.src.peek_u32be(); + if ret.is_err() || (common_header_word(ret.unwrap_or(0)) == common_header_word(self.frame_hdr)) { buf.push((ref_crc >> 8) as u8); buf.push(ref_crc as u8); break; -- 2.39.5