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Fix H.264 B-frame detection logic to comply with specification. v6.0.169 (#4414)

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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:
- 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>
This commit is contained in:
Haibo Chen(陈海博) 2025-07-10 21:08:05 +08:00 committed by winlin
parent 014812ea9b
commit 45090ce4fc
4 changed files with 6 additions and 3 deletions
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2
trunk/doc/CHANGELOG.md
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@ -7,6 +7,7 @@ The changelog for SRS.
<a name="v6-changes"></a>
## SRS 6.0 Changelog
* v6.0, 2025-07-10, Merge [#4414](https://github.com/ossrs/srs/pull/4414): Fix H.264 B-frame detection logic to comply with specification. v6.0.169 (#4414)
* v6.0, 2025-06-04, Merge [#4325](https://github.com/ossrs/srs/pull/4325): fix bug: loop transcoding #3516. v6.0.168 (#4325)
* v6.0, 2025-05-29, Merge [#4356](https://github.com/ossrs/srs/pull/4356): RTMP: Use extended timestamp as delta when chunk fmt=1/2. v6.0.167 (#4356)
* v6.0, 2025-03-21, Merge [#4303](https://github.com/ossrs/srs/pull/4303): replace values with enums. v6.0.165 (#4303)
@ -179,6 +180,7 @@ The changelog for SRS.
<a name="v5-changes"></a>
## SRS 5.0 Changelog
* v5.0, 2025-07-10, Merge [#4414](https://github.com/ossrs/srs/pull/4414): Fix H.264 B-frame detection logic to comply with specification. v5.0.224 (#4414)
* v5.0, 2025-03-21, Merge [#4303](https://github.com/ossrs/srs/pull/4303): replace values with enums. v5.0.223 (#4303)
* v5.0, 2025-03-20, Merge [#4305](https://github.com/ossrs/srs/pull/4305): free sample to prevent memory leak. v5.0.222 (#4305)
* v5.0, 2025-03-18, Merge [#4302](https://github.com/ossrs/srs/pull/4302): update geekyeggo/delete-artifact to 5.0.0. v5.0.221 (#4302)

2
trunk/src/core/srs_core_version5.hpp
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@ -9,6 +9,6 @@
#define VERSION_MAJOR 5
#define VERSION_MINOR 0
#define VERSION_REVISION 223
#define VERSION_REVISION 224
#endif

2
trunk/src/core/srs_core_version6.hpp
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@ -9,6 +9,6 @@
#define VERSION_MAJOR 6
#define VERSION_MINOR 0
#define VERSION_REVISION 168
#define VERSION_REVISION 169
#endif

3
trunk/src/kernel/srs_kernel_codec.cpp
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@ -725,7 +725,8 @@ srs_error_t SrsVideoFrame::parse_avc_b_frame(const SrsSample* sample, bool& is_b
return srs_error_wrap(err, "parse avc nalu type error");
}
if (nalu_type != SrsAvcNaluTypeNonIDR && nalu_type != SrsAvcNaluTypeDataPartitionA && nalu_type != SrsAvcNaluTypeIDR) {
if (nalu_type != SrsAvcNaluTypeNonIDR && nalu_type != SrsAvcNaluTypeDataPartitionA
&& nalu_type != SrsAvcNaluTypeDataPartitionB && nalu_type != SrsAvcNaluTypeDataPartitionC) {
is_b_frame = false;
return err;
}