Strip DVD private_stream_1 sub-stream header in PsExtractor#3328
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TsaiHao wants to merge 1 commit into
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Strip DVD private_stream_1 sub-stream header in PsExtractor#3328TsaiHao wants to merge 1 commit into
TsaiHao wants to merge 1 commit into
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In an MPEG Program Stream, AC-3 (and DTS/LPCM) audio is carried in private_stream_1 (PES stream id 0xBD). In DVD-style content each such PES packet begins with a 4-byte sub-stream header immediately after the PES header: sub_stream_id (0x80-0x87 AC-3, 0x88-0x8F DTS, 0xA0-0xA7 LPCM), number_of_frame_headers and first_access_unit_pointer. `PsExtractor.PesReader.consume()` stripped only the PES header and PTS/DTS extension, forwarding the sub-stream header straight into the audio reader as if it were elementary data. Because audio sync frames do not align to PES packet boundaries, these 4 bytes land inside the frame spanning each boundary and corrupt it, producing garbled audio (and decoder errors such as Dolby MS12 "UDC Node: Error extracting BSI metadata (err 1021)") when playing MPEG-PS content that VLC/ffmpeg play correctly. Skip the sub-stream header for private_stream_1 packets before handing the payload to the elementary stream reader, matching ffmpeg's mpegps demuxer. Adds a regression test with a small MPEG-PS asset whose AC-3 frames straddle PES boundaries (the existing single-packet sample_ac3.ps cannot expose this). Issue: androidx#3327
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In an MPEG Program Stream, AC-3 (and DTS/LPCM) audio is carried in private_stream_1 (PES stream id 0xBD). In DVD-style content each such PES packet begins with a 4-byte sub-stream header immediately after the PES header: sub_stream_id (0x80-0x87 AC-3, 0x88-0x8F DTS, 0xA0-0xA7 LPCM), number_of_frame_headers and first_access_unit_pointer.
PsExtractor.PesReader.consume()stripped only the PES header and PTS/DTS extension, forwarding the sub-stream header straight into the audio reader as if it were elementary data. Because audio sync frames do not align to PES packet boundaries, these 4 bytes land inside the frame spanning each boundary and corrupt it, producing garbled audio (and decoder errors such as Dolby MS12 "UDC Node: Error extracting BSI metadata (err 1021)") when playing MPEG-PS content that VLC/ffmpeg play correctly.Skip the sub-stream header for private_stream_1 packets before handing the payload to the elementary stream reader, matching ffmpeg's mpegps demuxer.
Adds a regression test with a small MPEG-PS asset whose AC-3 frames straddle PES boundaries (the existing single-packet sample_ac3.ps cannot expose this).
Issue: #3327