mirror of
https://github.com/freemkv/libfreemkv.git
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Matthew Jackson
6e14fc0c0c
Security - Remove the unsafe Vec::set_len over recycled sector buffers — UB reachable from safe code (GHSA-j8ww-f5fg-9pmh, low). Uses Vec::resize; pooling unchanged. CI / tooling - clippy on stable with the MSRV single-sourced from Cargo.toml; cargo-deny dependency-audit gate with first-party git sources allowed (#15); audience-based comment-guard (#17). Docs - README (keydb ownership, BD-J parser count), drive-access transport/reset notes, mux timeline module-doc links.
30 lines
1.3 KiB
Markdown
30 lines
1.3 KiB
Markdown
# BD/DVD LPCM wire format
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BD LPCM PES packets (TS stream type 0x80) carry a 4-byte header on the
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elementary-stream payload:
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```
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Bytes 0-1: audio frame number
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Byte 2: reserved
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Byte 3: quantization (bits 7-6), sample rate (bits 5-4), channel assignment (bits 3-0)
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```
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This header is part of the ES payload, so the BD parser must strip it.
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DVD LPCM lives in private stream 1 (sub-stream 0xA0-0xA7). Its 7-byte
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private sub-header (sub_id + frames + first-access-unit-ptr(2) + emphasis +
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quant/freq + channels) is stripped by `PsDemuxer` while demuxing the
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Program Stream. By the time a DVD LPCM `PesPacket` reaches this parser its
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`data` is already raw PCM, so the parser must NOT strip any further bytes —
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doing so drops one sample pair per PES and drifts the audio.
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The two origins are distinguished by the `strip_header` flag: BD = strip,
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DVD = leave intact. The raw PCM data is otherwise one complete audio frame
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per PES; no framing is needed.
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For MKV: both BD and DVD LPCM map to codec ID "A_PCM/INT/BIG" (big-endian).
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DVD-Video LPCM is big-endian per the DVD-Video spec, and `mkv.rs` emits
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"A_PCM/INT/BIG" unconditionally for `Codec::Lpcm` — there is no DVD/BD branch
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and no "A_PCM/INT/LIT" path, so no byte-swap or alternate codec ID applies.
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All frames are keyframes (uncompressed audio).
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