Fix H.264 B-frame detection logic to comply with specification. v5.0.224 v6.0.169 v7.0.46#4414
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winlinvip merged 5 commits intoossrs:developfrom Jul 10, 2025
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…224 (#4414) For H.264, only when the NAL Type is 1, 2, 3, or 4 is it possible for B-frames to be present; that is, non-IDR pictures and slice data. The current `SrsVideoFrame::parse_avc_bframe()` function uses incorrect logic to determine if a NALU can contain B-frames. The original implementation only checked for specific NALU types (IDR, SPS, PPS) to mark as non-B-frames, but this approach misses many other NALU types that cannot contain B-frames according to the H.264 specification. According to H.264 specification (ISO_IEC_14496-10-AVC-2012.pdf, Table 7-1), B-frames can **only** exist in these specific NALU types: - Type 1: Non-IDR coded slice (`SrsAvcNaluTypeNonIDR`) - Type 2: Coded slice data partition A (`SrsAvcNaluTypeDataPartitionA`) - Type 3: Coded slice data partition B (`SrsAvcNaluTypeDataPartitionB`) - Type 4: Coded slice data partition C (`SrsAvcNaluTypeDataPartitionC`) All other NALU types (IDR=5, SEI=6, SPS=7, PPS=8, AUD=9, etc.) cannot contain B-frames by definition. --------- Co-authored-by: Jacob Su <suzp1984@gmail.com> Co-authored-by: winlin <winlinvip@gmail.com>
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…169 (#4414) For H.264, only when the NAL Type is 1, 2, 3, or 4 is it possible for B-frames to be present; that is, non-IDR pictures and slice data. The current `SrsVideoFrame::parse_avc_bframe()` function uses incorrect logic to determine if a NALU can contain B-frames. The original implementation only checked for specific NALU types (IDR, SPS, PPS) to mark as non-B-frames, but this approach misses many other NALU types that cannot contain B-frames according to the H.264 specification. According to H.264 specification (ISO_IEC_14496-10-AVC-2012.pdf, Table 7-1), B-frames can **only** exist in these specific NALU types: - Type 1: Non-IDR coded slice (`SrsAvcNaluTypeNonIDR`) - Type 2: Coded slice data partition A (`SrsAvcNaluTypeDataPartitionA`) - Type 3: Coded slice data partition B (`SrsAvcNaluTypeDataPartitionB`) - Type 4: Coded slice data partition C (`SrsAvcNaluTypeDataPartitionC`) All other NALU types (IDR=5, SEI=6, SPS=7, PPS=8, AUD=9, etc.) cannot contain B-frames by definition. --------- Co-authored-by: Jacob Su <suzp1984@gmail.com> Co-authored-by: winlin <winlinvip@gmail.com>
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For H.264, only when the NAL Type is 1, 2, 3, or 4 is it possible for B-frames to be present; that is, non-IDR pictures and slice data.
The current
SrsVideoFrame::parse_avc_bframe()function uses incorrect logic to determine if a NALU can contain B-frames. The original implementation only checked for specific NALU types (IDR, SPS, PPS) to mark as non-B-frames, but this approach misses many other NALU types that cannot contain B-frames according to the H.264 specification.According to H.264 specification (ISO_IEC_14496-10-AVC-2012.pdf, Table 7-1), B-frames can only exist in these specific NALU types:
SrsAvcNaluTypeNonIDR)SrsAvcNaluTypeDataPartitionA)SrsAvcNaluTypeDataPartitionB)SrsAvcNaluTypeDataPartitionC)All other NALU types (IDR=5, SEI=6, SPS=7, PPS=8, AUD=9, etc.) cannot contain B-frames by definition.
Co-authored-by: Jacob Su suzp1984@gmail.com