fix mp4 stts box bug. #4190
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fix mp4 stts box bug. #4190
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xiaozhihong
reviewed
Oct 12, 2024
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| // skip any SEI type nalus | ||
| if (format->vcodec->id == SrsVideoCodecIdAVC) { |
xiaozhihong
reviewed
Oct 12, 2024
trunk/src/kernel/srs_kernel_mp4.cpp
Outdated
| if (stts && previous) { | ||
| if (sample->dts >= previous->dts && previous->nb_subsamples > 0) { | ||
| uint32_t delta = (uint32_t)(sample->dts - previous->dts) / previous->nb_subsamples; | ||
| stts_entry.sample_count = previous->nb_subsamples; |
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Sample in samples is an audio/video frame, nb_subsamples is the nalu count of this frame.
In most cases, it is always one nalu in one frame, but in multi-slice frames, there is more than one nalu in one video frame.
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nb_subsamples is a mistake. revert this code.
1. fix stts box calculation; 2. filter nalu SEI for h.265 codec.
xiaozhihong
reviewed
Oct 14, 2024
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| if (avc_nalu_type == SrsAvcNaluTypeSEI) { | ||
| return err; | ||
| } |
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If the video frame is [SEI P], will it drop? SEI always appears in Harward encoders like video toolbox, Nvidia enc, etc.
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How to reproduce?
./objs/srs -c conf/dvr.mp4.confffmpeg -re -i output.flv -c copy -f flv rtmp://localhost/live/livestreamthe
output.flvis recorded from a DJI drone, download from this google drive link: https://drive.google.com/file/d/1IVoDXI-WYoIlKiyzs65fCsDRRt0z-EuU/view?usp=sharinglivestream.*.mp4located intrunk/objs/nginx/html/live.Cause
The Mp4 frame rate is determined by mp4 box:
mdhdandstts. But thesttsencoding in srs has bugs. The aboveoutput.flvvideo file has a lot ofSEItype of nalu, which is not video samples, SRS can't calculate thesttscorrectly.How to calculate
stts?check doc ISO/IEC 14496-12:2012(E) 8.6.1.2 Decoding Time to Sample Box.
https://ossrs.net/lts/zh-cn/assets/files/ISO_IEC_14496-12-base-format-2012-b70dd5f101daecd072700609842c9649.pdf
video source generated by OBS with ultrafast + zerolatency
https://drive.google.com/file/d/1rXipV93EWmtZ-rPShwE66f5aO85ugiIc/view?usp=sharing
Use this source, with video frames split to multi slices, to verify the dvr recorded mp4.