>> On 07-10-2023 17:20, Ulf Zibis wrote: >>> Hi, >>> >>> what is the difference between i-frames and key frames? >>> >>> And how many other frames are between i-frames or key frames in mp4 >>> files, created with ffmpeg and with default settings? >>> >>> -Ulf >> In mp4 containers I-frames are key frames.> > >That is not correct. Via ffprobe, I have seen I-frames that were not marked >'key_frame=1'.
Firstly, the definition of what a key frame is may depend on contexts and on peoples, it is often a source of headaches. If you take a look at https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/h264_parser.c You can see that properly signaled recovery points are tagged as keyframes, which means you don't need an I-frame to make a keyframe (some low latency encoders make use of this). And you can also see that kind of things: // heuristic to detect non marked keyframes if (p->ps.sps->ref_frame_count <= 1 && p->ps.pps->ref_count[0] <= 1 && s->pict_type == AV_PICTURE_TYPE_I) s->key_frame = 1; as indeed, an I frame is not always a keyframe (long term references may be required later for further processing). And, at the end, sorry for not answering your question ;) Nicolas _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".