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• ffmpeg concatenate videos - what metadata needs to match [duplicate]

  13 juillet 2022, par yarrichar

  I am trying to concatenate videos that can come from a variety of sources.

  


  I was just using the -f concat option, but this runs into issues when the formats don't watch.

  


  I can use the filter_complex option (as described in the wiki - https://trac.ffmpeg.org/wiki/Concatenate) but this is much slower.

  


  What metadata (codec, bitrate, fps, etc) needs to match so that I can use the faster -f concat option to join the videos ? My understanding here is not great atm.

  


• Android Recorded Video Compression

  28 juillet 2014, par Nick Babenko

  This is a fairly long-winded issue and I’ve tried a couple of methods to fix it.

  The ultimate problem is the user records a video and the video is to be uploaded via a REST API. The original solution was to use the camera app and pass the user though via an Intent. This method requires very little configuration for video optimisation - using the MediaStore.EXTRA_VIDEO_QUALITY and value of 0 gives MMS optimisation, which makes the videos pretty much unusable and I was hoping for something a little more around 480p.

  So I started to create a custom video recorder using the MediaRecorder class. I managed to get this to work fine on a Nexus 4. I have 2 other test devices, a ZTE Blade and an Acer Iconica tab and it didn’t work with either of these devices.
  The ZTE Blade complained about an incorrect video size but the video size I was using was given by Camera.Parameters.getSupportedVideoSizes.
  The Acer Iconica tab didn’t have any valid CamcorderProfile’s. Calling CamcorderProfile.hasProfile on all of the available CamcorderProfile constants returned false. So if I was unsuccessful at loading a CamcorderProfile I attempted to configure MediaRecorder manually based on a device profile I found. This worked to an extent, but when I pressed record, I was presented with a black screen.

  The second solution was to use the existing camera intent solution, but then compress the video using FFMPEG. My experience of using the Android NDK is nil, so it was a bit of a challenge. I managed to compile a library which interfaces natively with FFMEG - this one specifically (https://github.com/Batterii/android-ffmpeg-x264). The Videokit class initialises, but when it comes to calling run with the following arguments :

  videoKit.run(new String[] {"ffmpeg", "-i", file.getAbsolutePath(), "-vf",
                       "scale=-1:480", "-vcodec", "mp3g4", "-qscale", "3",
                       outputFile.getAbsolutePath()});

  The app suddenly stops with no exception and almost nothing in the logs except that the activity suddenly stopped.

  The ultimate question I’ve been getting to is wether anyone has any solution to compress a video recorded on an Android device. If anyone can add to any of the issues I mentioned which hopefully will fix the issue, but I can’t quite get working then I will appreciate that even more.

  Thanks for reading and any help anyone has is incredibly appreciated.

• iPhone - A problem with decoding H264 using ffmpeg

  25 mars 2012, par HAPPY_TIGER

  I am working with ffmpeg to decode H264 stream from server.

  I referenced DecoderWrapper from http://github.com/dropcam/dropcam_for_iphone.

  I compiled it successfully, but I don't know how use it.

  Here are the function that has problem.

  - (id)initWithCodec:(enum VideoCodecType)codecType 
  
           colorSpace:(enum VideoColorSpace)colorSpace 
  
                width:(int)width 
  
               height:(int)height 
  
          privateData:(NSData*)privateData {
  
      if(self = [super init]) {
  
  
  
          codec = avcodec_find_decoder(CODEC_ID_H264);
  
          codecCtx = avcodec_alloc_context();
  
  
  
          // Note: for H.264 RTSP streams, the width and height are usually not specified (width and height are 0).  
  
          // These fields will become filled in once the first frame is decoded and the SPS is processed.
  
          codecCtx->width = width;
  
          codecCtx->height = height;
  
  
  
          codecCtx->extradata = av_malloc([privateData length]);
  
          codecCtx->extradata_size = [privateData length];
  
          [privateData getBytes:codecCtx->extradata length:codecCtx->extradata_size];
  
          codecCtx->pix_fmt = PIX_FMT_YUV420P;
  
  #ifdef SHOW_DEBUG_MV
  
          codecCtx->debug_mv = 0xFF;
  
  #endif
  
  
  
          srcFrame = avcodec_alloc_frame();
  
          dstFrame = avcodec_alloc_frame();
  
  
  
          int res = avcodec_open(codecCtx, codec);
  
          if (res < 0)
  
          {
  
              NSLog(@"Failed to initialize decoder");
  
          }
  
      }
  
  
  
      return self;    
  
  }

  What is the privateData parameter of this function ? I don't know how to set the parameter...

  Now avcodec_decode_video2 returns -1 ;

  The framedata is coming successfully.

  How solve this problem.

  Thanks a lot.