ffmpeg - less frames getting extracted than expected

0
votes

ffmpeg -i instagram.mp4 -vf fps=29.97 thumb%06d.jpg -hide_banner

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'instagram.mp4': Metadata: major_brand : isom minor_version : 512 compatible_brands: isomiso2avc1mp41 encoder : Lavf55.19.104 Duration: 00:00:13.61, start: 0.000000, bitrate: 1163 kb/s Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 640x640 [SAR 1:1 DAR 1:1], 1099 kb/s, 29.97 fps, 29.97 tbr, 11988 tbn, 59.94 tbc (default) Metadata: handler_name : VideoHandler Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 64 kb/s (default) Metadata: handler_name : SoundHandler Stream mapping: Stream #0:0 -> #0:0 (h264 (native) -> mjpeg (native)) Press [q] to stop, [?] for help [swscaler @ 0x55b2b53cf440] deprecated pixel format used, make sure you did set range correctly Output #0, image2, to 'thumb%06d.jpg':
Metadata: major_brand : isom minor_version : 512 compatible_brands: isomiso2avc1mp41 encoder : Lavf57.83.100 Stream #0:0(und): Video: mjpeg, yuvj420p(pc), 640x640 [SAR 1:1 DAR 1:1], q=2-31, 200 kb/s, 29.97 fps, 29.97 tbn, 29.97 tbc (default) Metadata: handler_name : VideoHandler encoder : Lavc57.107.100 mjpeg Side data: cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1 frame= 405 fps=231 q=24.8 Lsize=N/A time=00:00:13.51 bitrate=N/A speed=7.72x video:5961kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

The video duration is 13.61 seconds and frame rate is 29.97. So I was expecting 13.61 * 29.97 = 407.8917 i.e. 407 frames. But have got 405 frames. I am new to ffmpeg, need help to correctly get all 407 frames.

I had also tried following command,

ffmpeg -i instagram.mp4 thumb%06d.jpg -hide_banner

but the output was same 405 frames.

Possibly the start 2 frames are missing.

I need to display the frames generated in the base video timeline. And on clicking on the frame I need to exactly seek the video to the frame position using HTML5 currentTime. Since the first 2 frames are not getting available, exact mapping is not getting possible.

Please guide.

1
ffmpeg
Does the input video start with a keyframe? – Eugen Rieck
@EugenRieck Thanks for reply. How to recognize whether it starts with keyframe? – Vrajesh Doshi
The file duration shown is the duration for the longest stream. Check the duration for the video stream using ffmpeg -i instagram.mp4 -an -f null - – Gyan
@oguz ismail on executing the command no output got printed. i.e. the output was blank instead of 1. Is there a way to explicitly get all 407 frames of the video? – Vrajesh Doshi
@Gyan on executing your command I got the same duration. i.e. 13.61 sec. So right number of frames that I should get is 407 right? as per fps = 29.97. – Vrajesh Doshi

1 Answers

0
votes

have you try to use -vsync vfr or -vsync 0 disables the frame drop/dup behaviour? @Gyan Please refer to this question.

https://superuser.com/questions/1374584/why-does-ffmpeg-extracts-a-lot-more-frames-than-the-actual