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• How to pipe multiple images, being created in parallel with an index, to ffmpeg so that it can match the speed of image creation ?

  23 septembre 2020, par vishwas.mittal

  We've a system that spews out 4-channel png images frame-by-frame (we control the output format of these images as well, so we can use something else as long as it supports transparency). Right now, we're waiting for all the images and then encoding them with ffmpeg into a webm video file with vp8 (libvpx encoder). But we now want to pipeline these images to FFmpeg to encode into the WebM video simultaneously as the images are being spewed out so that we don't wait for ffmpeg to encode all the images afterwards.

  


  This is the current command, in python syntax :

  


  ['/usr/bin/ffmpeg', '-hide_banner', '-y', '-loglevel', 'info', '-f', 'rawvideo', '-pix_fmt', 'bgra', '-s', '1573x900', '-framerate', '30', '-i', '-', '-i', 'audio.wav', '-c:v', 'libvpx', '-b:v', '0', '-crf', '30', '-tile-columns', '2', '-quality', 'good', '-speed', '4', '-threads', '16', '-auto-alt-ref', '0', '-g', '300000', '-map', '0:v:0', '-map', '1:a:0', '-shortest', 'video.webm']
# for ease of read:
# /usr/bin/ffmpeg -hide_banner -y -loglevel info -f rawvideo -pix_fmt bgra -s 1573x900 -framerate 30 -i - -i audio.wav -c:v libvpx -b:v 0 -crf 30 -tile-columns 2 -quality good -speed 4 -threads 16 -auto-alt-ref 0 -g 300000 -map 0:v:0 -map 1:a:0 -shortest video.webm

proc = subprocess.Popen(args, stdin=subprocess.PIPE)


  


  Here is a sample example of passing the image to FFMPEG proc stdin as :

  


  # wait for the next frame to get ready
for frame_path in frame_path_list:
    while not os.path.exists(frame_path):
        time.sleep(0.25)
    frame = cv2.imread(frame_path, cv2.IMREAD_UNCHANGED)
    
    # put the frame in stdin so that it gets ready
    proc.stdin.write(frame.astype(np.uint8).tobytes())


  


  The current speed of this process is 0.135x which is a huge bottleneck for us. Earlier when we were taking input as -pattern_type glob -i images/*.png we were getting around 1x-1.2x for this on a single core. So, our conclusion is that we're getting bottlenecked by stdin and hence are looking for ways to pass input through multiple sources or somehow help ffmpeg to parallelize this effort - a few options that we're thinking of :

  


  

  • Somehow feed it to different pipes and make ffmpeg read from them.

  


  • Append a new image to ffmpeg without re-encoding the whole video, but we didn't find a way to do this with giving input images directly.

  


  


  But we haven't been able to get either of these working, open to any other solutions as well. Will really appreciate the help on this. Thanks !

  


• Elastic Transcoder output duration doesnt match with the sum of my Input duration

  28 mars 2019, par auricless

  I have multiple media file to concatenate into a single video file. Composed of different media types including video, audio and image. I use FFMPEG to convert audio and images to a video then finally, will use Elastic Transcoder to stitch/concatenate the video files in a single one. On creating transcoder job, whenever I placed the input video which is originally an image, converted by FFMPEG, to be the last input in order, it shrinks the duration of its exposure in the final output by 5 seconds whenever its original duration is > 5. This happens only with that condition.

  Example :
  (1) video1 - 10s
  (2) image1 - 10s
  (3) video2 - 15s
  (4) image2 - 20s
  output : video - 40s
  (image2’s duration or exposure in the output shrinks to approx. 5s)

  Clearly, the sum of Input duration and the Output duration does not match. It is even explicitly stated on the Job result of elastic transcoder.

  ---

  Thought I had a wrong conversion settings in FFMPEG so I changed some options. After some changes and comparing the image converted to video (V1) with an authentic video to stitch with (V2), their settings are almost the same. In this I use ffmpeg -i myVideo.mp4 to check its details. They differ only on SAR, DAR, tbr and tbn and I dont really know what are their use.

  Already checked the duration of the converted images after ffmpeg conversion and it is accurate, it only messed up after feeding it to the elastic transcoder and placed as the last input.

  Here is my conversion command with FFMPEG(image to video) :
  ffmpeg -r 29.97 -i [input.jpg] -f lavfi -i anullsrc=r=48000:cl:stereo -t [duration] -acodec aac -vcodec libx264 -profile:v baseline -pix_fmt yuv420p -t [duration] -vf scale=854:480 -strict -2 [output.mp4]

  The expected result should be that the output file is consistent with the actual duration it has.

  [EDIT]

  Here’s real videos I feed on Elastic Transcoder using ffprobe filename :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'clip2.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.71.100
  
    Duration: 00:00:10.05, start: 0.042667, bitrate: 476 kb/s
  
      Stream #0:0(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
      Stream #0:1(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 854x480 [SAR 2136:2135 DAR 89:50], 341 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'image2.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf56.12.100
  
    Duration: 00:02:10.03, start: 0.033333, bitrate: 130 kb/s
  
      Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 854x480 [SAR 1943:1004 DAR 829661:240960], 2636 kb/s, SAR 283440:146461 DAR 1181:343, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 128 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler

• ffmpeg Input link in1:v0 parameters do not match the corresponding output link in0:v0 parameters

  13 décembre 2017, par Anuj TBE

  I’m using ffmpeg to generate slideshow with images input from web

  ffmpeg  \
  
  -loop 1 -t 5 -i https://eample.com/image_1.jpg \
  
  -loop 1 -t 5 -i https://eample.com/image_2.jpg \
  
  -loop 1 -t 5 -i https://eample.com/image_3.jpg \
  
  -loop 1 -t 5 -i https://eample.com/image_4.jpg \
  
  -loop 1 -t 5 -i https://eample.com/image_5.jpg \
  
  -filter_complex \
  
  "[0:v]setdar=16/9,fade=t=out:st=4:d=1[v0]; \
  
   [1:v]setdar=16/9,fade=t=in:st=0:d=1,fade=t=out:st=4:d=1[v1]; \
  
   [2:v]setdar=16/9,fade=t=in:st=0:d=1,fade=t=out:st=4:d=1[v2]; \
  
   [3:v]setdar=16/9,fade=t=in:st=0:d=1,fade=t=out:st=4:d=1[v3]; \
  
   [4:v]setdar=16/9,fade=t=in:st=0:d=1,fade=t=out:st=4:d=1[v4]; \
  
   [v0][v1][v2][v3][v4]concat=n=5:v=1:a=0,format=yuv420p[v]" -map "[v]" out.mp4

  But after processing the videos, it gives error as

  [Parsed_concat_14 @ 0x3e5e9e0] Input link in1:v0 parameters (size 1024x709, SAR 709:576) do not match the corresponding output link in0:v0 parameters (500x281, SAR 1124:1125)
  
  [Parsed_concat_14 @ 0x3e5e9e0] Failed to configure output pad on Parsed_concat_14
  
  Error configuring complex filters.
  
  Invalid argument

  Is it related to scaling of images, since images could be different dimensions.

  Also, how to scale the images to fit 16:9 ratio may be using crop or fit ?