On 7/2/2025 7:57 AM, Timothee wrote:
Hello,I am working on a modification toextract per-macroblock prediction modes (H.264 for now). The goal is to make this information available to vf_codecview and print it in a log file (for now).This are what I have added: 1. A new H264MBInfostruct holding the prediction modes.
Isn't this what libavutil/video_enc_params.h is for? Or if needed, what it could be extended to handle?
2. An AVBufferRef *mb_info_refis added to the H264Picturestruct to store this data for each picture. 3. This buffer is allocated with av_buffer_allocz()in alloc_picture()and its reference is released with av_buffer_unref()in ff_h264_unref_picture(). 4. A new function, ff_h264_collect_mb_info(), is called after macroblock decoding to populate the buffer. 5. In output_frame(), a new side data (AV_FRAME_DATA_H264_MB_INFO) buffer is allocated, and the contents of srcp->mb_info_ref->dataare copied into it. 6. A new function to log the result in vf_codecview.cThis implementation results in a segmentation fault. I guess it is a race condition, but I am struggling to fix it.The patch provided should result in the same error when running `./ ffmpeg -loglevel debug -i input.mp4 -vf codecview=show_modes=1 -f null -`Are side data the right thing to use in this context ? Is there a better approach to do it ?I am new to FFmpeg and, in general, to large open-source projects, but I am willing to learn so please do not hesitate to correct me.Thank you for your guidance. Timothée _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
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