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• Right choice to play audio and video content

  22 juin 2012, par deimus

  What I'm doing :

  I need to play audio and video files that are not supported by Apple on iPhone/iPad for example mkv/mka files which my contain several audio channels.

  I'm using libffmpeg to find audio and video streams in media file.
  Video is being decoded with avcodec_decode_video2 and audio with avcodec_decode_audio3
  the return values are following for each function are following

  • avcodec_decode_video2 - returns AVFrame structure which encapsulates information about the video video frame from the pakcage, specifically is has data field which is a pointer to the picture/channel planes.
  • avcodec_decode_audio3 - returns samples of type int16_t * which I guess is the raw audio data

  So basically I've done all this and successfully decoding the media content.

  What I have to do :
  I've to play the audio and video accordingly using Apples services. The playback I need to perform should support mixing of audio channels while playing video, i.e. let say mkv file contains two audio channel and a video channel. So I would like to know which service will be the appropriate choice for me ? My research showed that AudioQueue service might be useful audio playback, and probably AVFoundation for video.

  Please help to find the right technology for my case i.e. video playeback + audio playback with possible audio channel mixing.

• Create and update HLS playlist programmatically

  26 février 2018, par Pierre P.

  I have a C++ application that records audio from my default input device, encodes it in AAC format and writes to a .aac file. I want to use HTTP Live Streaming to live stream this AAC file. According to this question, I have to create a FFMPEG script to split my audio file into several .ts files.

  # bitrate, width, and height, you may want to change this
  
  BR=512k
  
  WIDTH=432
  
  HEIGHT=240
  
  input=${1}
  
  
  
  # strip off the file extension
  
  output=$(echo ${input} | sed 's/\..*//' )
  
  
  
  # works for most videos
  
  ffmpeg -y -i ${input} -f mpegts -acodec libmp3lame -ar 48000 -ab 64k -s ${WIDTH}x${HEIGHT} -vcodec libx264 -b ${BR} -flags +loop -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 -subq 7 -trellis 0 -refs 0 -coder 0 -me_range 16 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -bt 200k -maxrate ${BR} -bufsize ${BR} -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.6 -qmin 30 -qmax 51 -qdiff 4 -level 30 -aspect ${WIDTH}:${HEIGHT} -g 30 -async 2 ${output}-iphone.ts

  (It is slightly different in my case because I only work with audio)

  Can I do so programmatically in C++ and if so, do I have to use a third-part library or does macOS provide native functions to do so ?

• Encoding video settings with Transloadit and FFMPEG

  2 octobre 2015, par David Soler

  I’m using Transloadit to convert and compress videos from .mov to .ts format. I’m using the json templates but unfortunately the docs are not too extensive. The thing is the quality I’m getting rigth now is very poor and pixeled. If I do it through console with ffmpeg command and including some parameters as crf (Constant Rate Factor) the quality gets a lot better but I dont know how edit it in transloadit template to get the same result.

  This is the ffmpeg command I’m using to convert the video in console

  ./ffmpeg -i ../canales.mov -c:v libx264 -crf 23 -bsf:a aac_adtstoasc output.ts

  And this is the json template I’m using right now. I guess I should add parameters to ffmpeg hash but I don’t know which settings are allowed

  {
  
    "steps": {
  
      "file": {
  
        "robot": "/file/filter",
  
        "accepts": [
  
          [
  
            "${file.mime}",
  
            "regex",
  
            "video"
  
          ]
  
        ],
  
        "declines": [
  
          [
  
            "${file.size}",
  
            ">",
  
            "10485760"
  
          ],
  
          [
  
            "${file.meta.duration}",
  
            ">",
  
            "16"
  
          ]
  
        ],
  
        "error_on_decline": true
  
      },
  
      "segments": {
  
        "robot": "/video/encode",
  
        "preset": "iphone-high",
  
        "width": 1242,
  
        "height": 2208,
  
        "use": "file",
  
        "segment": true,
  
        "segment_duration": 10,
  
        "ffmpeg_stack": "v2.2.3",
  
        "ffmpeg": {
  
          "b": "1200K",
  
          "crf": 23
  
        }
  
      },
  
      "thumb": {
  
        "robot": "/video/thumbs",
  
        "use": "file",
  
        "count": 1
  
      },
  
      "store": {
  
        "robot": "/s3/store",
  
        "use": [
  
          "segments",
  
          "thumb"
  
        ],
  
        "key": "key",
  
        "secret": "Secret",
  
        "bucket": "bucket"
  
      }
  
    }
  
  }