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• ffmpeg - less frames getting extracted than expected

  20 juin 2021, par Vrajesh Doshi

  


  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.

  


• Stacking videos with ffmpeg via MATLAB not working as expected

  18 juillet 2022, par ersatzsheep

  I am stacking 4 video inputs in a 2x2 grid and running into a conversion failure.

  


  Basically, at least one of the videos is just a filler black video that I generated with this line (MATLAB, hence the eval) :

  


  eval(['!ffmpeg -framerate 1/3600 -i black_frame.JPG -c:v libx264 -t 3600 -pix_fmt yuv420p -vf scale=320:240 black_frame.mp4']);


  


  The other video inputs are 4 hr long videos with identical specs. I've concatenated them with this line :

  


  eval(['!ffmpeg -i "' v1 '" -i "' v3 '" -i "' v2 '" -i "' v4 '" -filter_complex "  [0:v] setpts=PTS-STARTPTS, scale=qvga [a0]; [1:v] setpts=PTS-STARTPTS, scale=qvga [a1]; [2:v] setpts=PTS-STARTPTS, scale=qvga [a2];  [3:v] setpts=PTS-STARTPTS, scale=qvga [a3];  [a0][a1][a2][a3]xstack=inputs=4:layout=0_0|0_h0|w0_0|w0_h0[out] "  -map "[out]" -c:v libx264 "' output '"'])  


  


  When I input v1-v4 with normal videos (not the filler black video), it outputs very quickly and everything is good. The line to generate the filler black video is very fast too. But when I sub one of the video inputs with the file path for the filler black video, the speed tanks exponentially, stalls, and conversion fails.

  


  Any pointers for me ? I also tried just subbing one of the inputs with a black image file instead of generating a whole video and inputting that. But it does the same thing :/ Does it have to do with frame rate ? Should I try a different approach ? Thanks.

  


• The built ffmpeg.exe is not working as expected

  29 avril 2021, par user1939578

  In my c++ application, I want to use ffmpeg lib statically.

  


  I downloaded the ffmpeg-3.4.1 source and built the statically linked ffmpeg using MINGW, Yasm and VS2015 Command prompt as follows,

  


  

  1. Downloaded the msys2-x86_64-20161025.exe

  


  2. On opening the MINGW command prompt, install the required gcc tool using command "pacman -S make gcc diffutils"

  


  3. Renamed C :\msys64\usr\bin\link.exe to C :\msys64\usr\bin\link_orig.exe

  


  4. Downloaded the yasm 32 bit exe and set it's path to PATH environment variable. ("%PATH% ;D :\ffmpeg")

  


  5. Run VS2015, and open MINGW- C :\msys64\msys2_shell.cmd -use-full-path

  


  6. On opening MingW, change pwd to ffmpeg. Run ./configure then make the make install.

  


  


  The configuration is used : ./configure —prefix="build" —toolchain=msvc —arch=x86 —enable-yasm —enable-asm —disable-shared —enable-static

  


  It is built successfully. I got the bin folder having ffmpeg.exe and ffprobe.exe. The size of ffmpeg.exe is 18 Mb. Also the 7 libs as .a file.

  


  I guess I have to convert.a files to .lib and use in application ?

  


  I wanted to confirm if I have built everything correctly. So I tried to convert a .webm file to mp4 using the built ffmpeg.exe. I found that the size of output file is very large and quality is too bad. The input.webm file size was only 15 Mb and output.mp4 file size was about 188 Mb.

  


  Then I downloaded the statically link ffmpeg application from https://ffmpeg.zeranoe.com/builds/. I see the size of ffmpeg.exe is about 35 Mb and It works fine. For same .webm file, it created .mp4 file only 44 Mb and quality is also ok. I figured out that it is built with lots of external libs.

  


  Are external libs creating the difference or my built ffmpeg application is not right ? Do I need all those libs in my application too in order to get similar output ?

  


  screenshot output.mp4 from built ffmpeg.exe(15 Mb)