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• Recording with libx264 results in audio muting prior to recording being stopped depending on preset

  24 janvier 2020, par Pyon

  ffmpeg -thread_queue_size 512 -f dshow -i audio="AudioDevice" -thread_queue_size 512 -f gdigrab -rtbufsize 100000000 -hwaccel auto -framerate 60 -offset_x 332 -offset_y 720 -video_size 340x162 -probesize 10000000 -i desktop -c:v libx264 -preset veryslow -crf 23 -pix_fmt yuv420p "output.mp4"

  I’m using the above command to record desktop video/audio in a defined region.
  The video is being recorded using gdigrab while the audio is being recorded using dshow with a custom loopback driver.

  When the libx264 preset is set to anything below "ultrafast" like "veryslow", the audio will be muted around 80% into the recording (varies depending on video size and the preset selected, worsening for slower presets). By muted I mean : If I record a 10 second video, the video will be 10 seconds in length but the audio will only be audible for the first 8 seconds.

  I’m not really sure what could be causing this, but is there any way around it ?

  Below are simplified versions which produces same results..

  Veryslow preset (audio issue) :

  ffmpeg -thread_queue_size 512 -f dshow -i audio="PriAudio" -thread_queue_size 512 -f gdigrab -i desktop -c:v libx264 -preset veryslow -crf 23 -pix_fmt yuv420p "output.mp4"

  Ultrafast preset (no audio issue) :

  ffmpeg -thread_queue_size 512 -f dshow -i audio="PriAudio" -thread_queue_size 512 -f gdigrab -i desktop -c:v libx264 -preset ultrafast -crf 23 -pix_fmt yuv420p "output.mp4"

  I don’t want to use ultrafast because it results in poor quality/compression ratio.

• ffmpeg read from a file and apply filter_complex at once

  30 janvier 2020, par AlexZheda

  I am feeding fls.txt into ffmpeg -i and applying concat and a speedup.

  fls.txt

  file 'input1.mp4'
  
  file 'input2.mp4'
  
  file 'input3.mp4'

  The command in one go looks as follows :

  ffmpeg  -i fls.txt     \
  
  -filter_complex "[0:v][0:a][1:v][1:a][2:v][2:a] concat=n=3:v=1:a=1 [v][a];\
  
  [v]setpts=0.5*PTS[v1];[a]atempo=2,asetpts=N/SR/TB[a1]"     \
  
  -c:v h264_nvenc -map "[v1]" -map "[a1]"  x2.mp4

  The output is really weird and says something like a stream is not found. And it also looks like as if it’s trying to understand the fls.txt itself and not its content as the parameters.
  What am I doing wrong here and how can I correct it ?
  Also, it’s a simplified example and I cannot write per hand 3 input file paths. I need it to be read from a file. I’m on windows 10 if that matters.

  EDIT :
  From doing the suggested edits and expanding the -filter_complex I get an error below.

  ffmpeg -f concat -safe 0 -i fls.txt     \
  
  -filter_complex "[0:v]setpts=0.5*PTS[v1];[v1]setpts=0.5*PTS[v2];[0:a]atempo=2,asetpts=N/SR/TB[a1];[a1]atempo=2,asetpts=N/SR/TB[a2]"     \
  
  -c:v h264_nvenc -map "[v1]" -map "[a1]" x2.mp4 \
  
  -c:v h264_nvenc -map "[v2]" -map "[a2]" x4.mp4

  error :

  Output with label 'v1' does not exist in any defined filter graph, or was already used elsewhere.

• Conversion failed. 2 frames left in the queue on closing ffmpeg

  28 août 2020, par AlexZheda

  My simplified ffmpeg command (the longer one has over 300 files) is the following.

  



  ffmpeg -i "v1.mp4" -i "v2.mp4" -i "v3.mp4"
    -filter_complex "[0:v:0][1:v:0][2:v:0]concat=n=3:v=1:a=0,fps=fps=30[cv1]; 
        [0:a:0][1:a:0][2:a:0]concat=n=3:v=0:a=1,asetpts=N/SR/TB[ca1]; 
        [cv1]setpts=0.25*PTS[v4]; 
        [ca1]atempo=4,asetpts=N/SR/TB[a4]" 
    -c:v h264_nvenc -map "[v4]" -map "[a4]" x4_output_0.mp4


  



  The video encoding is working but then breaks and the output file seems to be truncated. The output files are nearly of the size as they should be but they can't be read.

  



  Video encoding failed\r\n
[aac @ 00000248a7856840] Qavg: 325.600\r\n
[aac @ 00000248a7856840] 2 frames left in the queue on closing\r\n
[aac @ 00000248a78595c0] Qavg: 236.279\r\n[aac @ 00000248a78595c0] 
2 frames left in the queue on closing\r\n
[aac @ 00000248a7855140] Qavg: 2729.299\r\n
[aac @ 00000248a7855140] 2 frames left in the queue on closing\r\n
[aac @ 00000248a785bec0] Qavg: 1158.664\r\n
[aac @ 00000248a785bec0] 2 frames left in the queue on closing\r\n
Conversion failed!\r\n")


  



  

  1. Does the error have anything to do with the audio part of .mp4 since aac @ ... ?

  


  2. What does the Qavg mean in the error message ?

  


  3. What is the difference in the video stream between the codec_time_base and the time_base (see the differences in the video attributes frequencies below) ?

  


  



  Below are the frequencies of the video attributes for all videos that have more than 1 distinct value. It's of the form [(value, frequency), (value, frequency),...].

  



  codec_time_base --- [('1/60', 384), ('1001/60000', 7), ('50/2997', 1)]
has_b_frames --- [(0, 336), (2, 56)]
level --- [(31, 336), (30, 56)]
r_frame_rate --- [('30/1', 384), ('30000/1001', 7), ('2997/100', 1)]
avg_frame_rate --- [('30/1', 384), ('30000/1001', 7), ('2997/100', 1)]
time_base --- [('1/30', 383), ('1/30000', 7), ('1/2997', 1), ('1/15360', 1)]


  



  The same for the audio attributes in all those video files.

  



  codec_time_base --- [('1/48000', 386), ('1/44100', 6)]
sample_rate --- [('48000', 386), ('44100', 6)]
time_base --- [('1/48000', 386), ('1/44100', 6)]


  



  

  4. Is it possible that something is not right with some of the video files here that causes the breakdown of the encoding ?