Recherche avancée

Sur d’autres sites (14164)

• Decoding AAC to PCM with ffmpeg results in noise

  18 octobre 2022, par userDtrm

  I have a .mp4 file generated with ffmpeg as follows.

  


  


  ffmpeg -y -i video_extended.mp4 -itsoffset 00:00:04.00 -i output5-1.wav -map 0:0 -map 1:0 -c:v copy -c:a aac -ac 6 -ar 48000 -b:a 128k -async 1 mixed.mp4

  


  


  Playing mixed.mp4 file with ffplay is fine and there is no impact to the sound quality. Below is the output I get from ffplay when using the command ffplay -i  mixed.mp4

  


  > Input #0, mov,mp4,m4a,3gp,3g2,mj2, from
> 'mixed_h264_aac_512k_async_qp0_all_I.mp4':   Metadata:
>     major_brand     : isom
>     minor_version   : 512
>     compatible_brands: isomiso2avc1mp41
>     encoder         : Lavf58.76.100   Duration: 00:00:16.02, start: 0.000000, bitrate: 49136 kb/s   Stream #0:0[0x1](und): Video: h264 (High 4:4:4 Predictive) (avc1 / 0x31637661), yuv422p10le(progressive),
> 1920x1080, 65409 kb/s, 59.94 fps, 59.94 tbr, 11988 tbn (default)
>     Metadata:
>       handler_name    : VideoHandler
>       vendor_id       : [0][0][0][0]   Stream #0:1[0x2](und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 71 kb/s (default)
>     Metadata:
>       handler_name    : SoundHandler
>       vendor_id       : [0][0][0][0] Switch subtitle stream from #-1 to #-1 vq= 1606KB sq=    0B f=0/0


  


  Then, I decode the mixed.mp4 file back to raw PCM using the following command.

  


  


  ffmpeg -i mixed.mp4 -vn -acodec pcm_s16le -f s16le -ar 48000 -ac 6 raw_audio.pcm

  


  


  However, this raw_audio.pcm contains a lot of noise and ffplay output shows the following output

  


  [s16le @ 0x7f7490000c80] Estimating duration from bitrate, this may be inaccurate
Input #0, s16le, from 'separated_audio_s16.pcm':
  Duration: 00:00:16.02, bitrate: 4607 kb/s
  Stream #0:0: Audio: pcm_s16le, 48000 Hz, 6 channels, s16, 4608 kb/s
[pcm_s16le @ 0x7f749002b940] Multiple frames in a packet.
[pcm_s16le @ 0x7f749002b940] Invalid PCM packet, data has size 8 but at least a size of 12 was expected
    Last message repeated 32 times
[pcm_s16le @ 0x7f749002b940] Invalid PCM packet, data has size 8 but at least a size of 12 was expected
    Last message repeated 11 times
Switch subtitle stream from #-1 to #-1 vq=    0KB sq=    0B f=0/0   
[pcm_s16le @ 0x7f749002b940] Invalid PCM packet, data has size 8 but at least a size of 12 was expected
    Last message repeated 11 times
[pcm_s16le @ 0x7f749002b940] Invalid PCM packet, data has size 8 but at least a size of 12 was expected
    Last message repeated 11 times
[pcm_s16le @ 0x7f749002b940] Invalid PCM packet, data has size 8 but at least a size of 12 was expected


  


  Can someone please explain the issue here ? Note that the ffplay command that works correctly for mixed.mp4 shows fltp as the audio format, whereas when playing the raw_audio.pcm file, it is seen as s16.

  


  Is this a resampling issue in ffmpeg, and how can I rectify this ?

  


  I’m using ffmpeg and ffplay versions 5.0.1 in a Fedora 36 system.

  


  Thank you.

  


• Killing ffmpeg from Qt results in a corrupt video file

  21 octobre 2014, par parsley72

  I’m using Qt to record stream data from a Mobotix camera on Windows 7. The command I use is :

  ffmpeg -f mjpeg -i "http://admin:password@192.168.0.100/control/faststream.jpg?stream=full" -c:v libx264 -preset slow -crf 22 -c:a copy out.mp4

  This works fine from the command line and when I want to stop it I just do Ctrl-C. But I’m doing this from an application using Qt 5.2 via a QProcess. After 10 minutes I want to stop the recording so I tried QProcess::terminate() but this doesn’t stop it. QProcess::kill() works but the resulting video won’t play. This answer suggests I’m doing it the right way.

  I connect to QProcess::finished() so when I call QProcess::kill() the result is :

  • int exitCode = 62097
  • QProcess::ExitStatus exitStatus = QProcess::CrashExit

  Apparently this is the return code Qt uses when it kills a process.

  So is there any other way for me to either terminate the process gracefully (the same as pressing Ctrl-C) or perform this same functionality via an ffmpeg library so I can stop it properly ?

• Rails : Paperclip produces different results for similar videos

  10 décembre 2016, par Polyov

  I am using the Paperclip Gem to handle video uploads on my Rails app. I’ve followed the instructions in a few other stackoverflow questions and external tutorials to get video uploads working. However, currently there is a strange glitch with the system that I don’t understand.

  When uploading two different videos, the app will be able to show a thumbnail and no video for one upload, and no thumbnail but video for another one.

  Both videos use the same codecs, are around the same length, but are a bit different in their dimensions & file size.

  

  When I upload them, test1 has a thumbnail, but my browser will not load the video file. It exists in my file system but Chrome will not play it.

  The opposite happens for test2. Its thumbnail in my file system is zero bytes, but the video loads fine in my browser.

  Here are the paperclip upload parameters for my object :

  has_attached_file :video, :styles => {
  
      :medium => { :format => 'mp4' },
  
      :thumb => { :geometry => "500x500#", :format => 'jpg', :time => 10 }
  
    }, :processors => [:transcoder]
  
  validates_attachment_presence :video
  
  validates_attachment :video, content_type: { content_type: ["video/mp4", "video/mov", "video/wav", "video/wmv"] }

  I’ve created a Github repo with an example app that reproduces the issue, at least on my system.