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• Using OpenMAX (IL ?) for audio/video decoding on Android

  14 septembre 2012, par Christopher Corsi

  Many of the newer hardware platforms running Android, in particular NVIDIA's Tegra 2, support OpenMAX for media acceleration. It's effectively impossible on today's devices to decode 720p video without this support, but the number of demuxers supported on Android are quite slim. The only public API I've been able to find has been through the MediaPlayer class in the Android SDK. There are multiple places in the Android source tree with OpenMAX related tidbits, however.

  On my device (Samsung Galaxy Tab 10.1) I've got access to hardware decoders through a multitude of OpenMAX libs in /system/lib, and it would be great to interface my video application with these. Can anyone point me to information on implementing a decoder powered by OpenMAX ? I've found the documentation from Khronos, but nothing in the way of example code or tutorials. I've already got demuxing and even software decoding taken care of (via libavcodec/libavformat), I'd just like to put hooks in to enable hardware encoding. I'm also assuming here it would be necessary to link directly to the ones available on the device, which makes it pretty lackluster in terms of portability, but it works.

  Alternatively, I'm interested in anything anyone knows about private APIs for accessing the video decoding available on Tegra 2 devices. Especially if there's a vdpau interface like what NVIDIA implements for desktop linux distributions, since there's plenty available for that - but I wasn't able to find shared libraries that indicate that support.

• ffprobe returns mov,mp4,m4a,3gp,3g2,mj2

  19 octobre 2015, par sathia

  I’m trying to find a certain way to understand if a given file is using the h.264 codec and it’s streamable.

  I’m using ffprobe and sometimes I get output such as this :

  {
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'file.mp4':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      creation_time   : 2036-02-06 06:28:16
  
      encoder         : HandBrake 0.10.2 2015060900
  
    Duration: 00:06:42.13, start: 0.000000, bitrate: 950 kb/s
  
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, smpte170m/smpte170m/bt709), 640x480 [SAR 1:1 DAR 4:3], 788 kb/s, 30 fps, 30 tbr, 90k tbn, 180k tbc (default)
  
      Metadata:
  
        creation_time   : 2036-02-06 06:28:16
  
        handler_name    : VideoHandler
  
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 155 kb/s (default)
  
      Metadata:
  
        creation_time   : 2036-02-06 06:28:16
  
        handler_name    : Stereo
  
      "format": {
  
          "filename": "file.mp4",
  
          "nb_streams": 2,
  
          "nb_programs": 0,
  
          "format_name": "mov,mp4,m4a,3gp,3g2,mj2",
  
          "format_long_name": "QuickTime / MOV",
  
          "start_time": "0.000000",
  
          "duration": "402.134000",
  
          "size": "47787790",
  
          "bit_rate": "950683",
  
          "probe_score": 100,
  
          "tags": {
  
              "major_brand": "mp42",
  
              "minor_version": "512",
  
              "compatible_brands": "isomiso2avc1mp41",
  
              "creation_time": "2036-02-06 06:28:16",
  
              "encoder": "HandBrake 0.10.2 2015060900"
  
          }
  
      }
  
  }

  now, it seems that the file is streamable and it’s ok to be put online, but I was expecting something like this :

      "format_name": "h.264",

  instead I get

      "format_name": "mov,mp4,m4a,3gp,3g2,mj2",

  which seems very lax in terms of specifying what the hell this file is.
  I’m also using MP4Box in order to see if the video is streamable, but at this point I’m not sure how to handle specific h.264 recognition.

  what should I do in order to be sure that a given file has the h.264 codec ?

  thanks

• How to concat videos that have different colour spaces ?

  17 avril 2023, par Ham789

  I writing a Python program that uses subprocess to automate ffmpeg. The program concatenates many videos together with the concat filter. The problem I have is that the colour of some of the videos is very washed out in the final output. I believe this is because the videos have different colour spaces. Some are B.709 and some are B.2020. The B.2020 videos are washed out.

  


  I have tried converting the B.2020 videos to B.709 before concatenating by using the following command on each video but the outputs are still washed out :

  


  ffmpeg -i input.mov -vf colorspace=all=bt709:iall=bt2020:fast=1 output.mov


  


  It wasn't clear to me which way round the arguments should go so I also tried switching the bt2020 and bt709 terms but they still look washed out but with more saturation.

  


  Is this the right approach ? Am I missing some other arguments in order to convert the B.2020 videos to B.709 while preserving their colour ?

  


  I have attached a side by side of the original and converted video.

  


  The metadata of the videos I am trying to concat are :

  


  Video 1

  


  

  • color_range=tv

  


  • color_space=bt709

  


  • color_transfer=bt709

  


  • color_primaries=bt709

  


  


  Video 2

  


  

  • color_range=tv

  


  • color_space=bt2020nc

  


  • color_transfer=arib-std-b67

  


  • color_primaries=bt2020