Newest 'ffmpeg' Questions - Stack Overflow

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• Can I force FFMPEG to insert keyframes every second ?

  6 octobre 2011, par Kristian Frost

  I'm converting a bunch of videos to FLV with FFmpeg, and I've found the -force_key_frames option in the FFmpeg documentation.

  I want to insert a keyframe every second of the video, to enable smooth seeking. Is there any (easy) way to tell FFmpeg that I want a keyframe every second?

• Python/FFMPEG command line issues

  5 octobre 2011, par 12hys

  I have a problem with running an FFMPEG command from within a Python script. When I run the following command from the terminal, I can stream video and audio from my attached webcam (Logitech C310) and output to file "out.avi" without any errors.

  ffmpeg -f alsa -i default -itsoffset 00:00:00 -f video4linux2 -s 1280x720 -r 25 -i /dev/video0 out.avi
  

  When I run the same command in a Python script below,

  def call_command(command):
      subprocess.Popen(command.split(' '))
  
  call_command("ffmpeg -f alsa -i default -itsoffset 00:00:00 -f video4linux2 -s 1280x720 -r 25 -i /dev/video0 out.avi")
  

  it gives me the error:

  Input #0, alsa, from 'default':
    Duration: N/A, start: 1317762562.695397, bitrate: N/A
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, 1 channels, s16, 705 kb/s
  [video4linux2 @ 0x165eb10]Cannot find a proper format for codec_id 0, pix_fmt -1.
  /dev/video0: Input/output error
  

  Could anyone shed some light on what could be going on here? I've tried using os.system() as well as subprocess.call() and it gives me the same errors. I'm not sure where to start on what could be going wrong here. I tried searching for the "video4linux2 Cannot find a proper format for codec_id 0, pix_fmt -1" error, but couldn't find anything consistent.

  I've also tried putting the "ffmpeg -f..." command in a shell script "test.sh", and giving it executable permissions. I then open terminal, and run "./test.sh", and it works. When I try calling the command "./test.sh" from within my Python script, I'm left with the original error as before. This is the Python command I tried with the test.sh script:

  subprocess.call(["./test.sh"])
  

• iPad Doesn't Render H.264 Video with HTML5

  5 octobre 2011, par jgoldberg

  I have some H.264-encoded videos which render in HTML5 correctly in the web browser, but do not render correctly on the iPad. When I use a H.264 video I downloaded off the internet, my video renders correctly on the iPad, so it is not an HTML problem.

  Here is the ffmpeg info about my videos --

  My original .mov video:

  Seems stream 1 codec frame rate differs from container frame rate: 6000.00 (6000/1) -> 30.00 (30/1)

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'a_video.mp4':

  Metadata:

  major_brand     : qt  
  minor_version   : 537199360
  compatible_brands: qt  
  

  Duration: 00:00:42.74, start: 0.000000, bitrate: 220 kb/s

  Stream #0.0(eng): Audio: aac, 44100 Hz, stereo, s16, 94 kb/s
  Stream #0.1(eng): Video: h264, yuv420p, 762x464, 122 kb/s, 30 fps, 30 tbr, 3k tbn, 6k tbc
  

  After using Handbrake to convert my .mov to a mp4, yet doesn't render on the iPad:

  Seems stream 0 codec frame rate differs from container frame rate: 180000.00 (180000/1) -> 29.97 (30000/1001)

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'a_video.m4v':

  Metadata:

  major_brand     : mp42  
  minor_version   : 0
  compatible_brands: mp42isomavc1  
  encoder: HandBrake 0.9.5 2011010300  
  

  Duration: 00:00:42.77, start: 0.000000, bitrate: 169 kb/s

  Stream #0.0(und): Video: h264, yuv420p, 752x464 [PAR 381:376 DAR 381:232], 35 kb/s, PAR 145161:141376 DAR 145161:87232, 29.97 fps, 29.97 tbr, 90k tbn, 180k tbc
  Stream #0.1(eng): Audio: aac, 44100 Hz, stereo, s16, 128 kb/s

  Here is a .mp4 I found online which does render on the iPad:

  Seems stream 1 codec frame rate differs from container frame rate: 180000.00 (180000/1) -> 25.00 (25/1)

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'a_video_3_emu.mp4':

  Metadata: major_brand : M4VP
  minor_version : 1
  compatible_brands: M4VPM4A mp42isom
  encoder : CoreMediaAuthoring 677, CoreMedia 420.17, i386

  Duration: 00:01:38.01, start: 0.000000, bitrate: 1023 kb/s

  Stream #0.0(und): Audio: aac, 32000 Hz, mono, s16, 97 kb/s
  Stream #0.1(und): Video: h264, yuv420p, 480x360 [PAR 1:1 DAR 4:3], 914 kb/s, 25 fps, 25 tbr, 90k tbn, 180k tbc

  Does anyone see something wrong with the way I am encoded my videos?

  Edit

  At first my theory was that the iPad was sensitive to different container formats; but that appears not to be the case. I took a video which does render correctly on the iPad and converted it to a .mov, and it still played correctly on the iPad. So there must be a problem with how the iPad deals with the underlying H.264 stream.

• How to display and capture webcam stream at the same time ? [migrated]

  5 octobre 2011, par 12hys

  This command works perfectly for saving a webcam stream to a file:

  ffmpeg -f alsa -i default -itsoffset 00:00:00 -f video4linux2 -s 1280x720 -r 25 -i /dev/video0  out.avi
  

  How would I simultaneously display this captured stream on my computer screen?

• A way to convert bitrate/format of audio files (between upload & storage to S3)

  5 octobre 2011, par Jonathan Coe

  Currently using PHP 5.3.x & Fedora

  Ok. I'll try to keep this simple. I'm working on a tool that allows the upload & storing of audio files on S3 for playback. Essentially, the user uploads a file (currently only allowing mp3 & m4a) to the server, and the file is then pushed to S3 for storage via the PHP SDK for amazon aws.

  The missing link is that I would like to perform a simple bitrate & format conversion of the file prior to uploading the file. (ensuring that all files are 160kbs and .mp3).

  I've looked into ffmpeg, although it seems that the PHP library only allows for reading bitrates and other meta, not for actual conversion.

  Does anyone have any thoughts on the best way to approach this? Would running a shell_exec() command that performs the conversion be sufficient to do this, or is there a more efficient/better way of doing this?

  Thanks in advance! Any help or advice is much appreciated.