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• FFMPEG best practice ?

  26 avril 2013, par HighFlyingFantasy

  I'm trying to write a wrapper class for FFMPEG. I have 4 classes within the wrapper, Stream, Demux, Encode, Decode. All of these classes use avcodec, avformat, etc. My question is, can I use the avcodec_register_all, av_register_all and avformat_network_init in my top level wrapper after initializing the lower level classes, or should I call each one individually in the lower level init methods ?

• Will ffmpeg transcoding change the media's duration ?

  6 juillet 2012, par MaiTiano

  For example, I have a example flv media : 1775818137_1775828481_10344.flv. Only audio data has contained in it. (No video data)

  The major properties of this flv are :

  _____________________________________________________________________
  
  Format                                   : Flash Video
  
  
  
  File size                                : 87.4 KiB
  
  
  
  Duration                                 : 494 hours
  
  
  
  Overall bit rate mode                    : CBR
  
  
  
  Overall bit rate                         : 0 bps
  
  
  
  Writing application                      : Lavf53.4.0
  
  
  
  Audio
  
  
  
  Format                                   : MPEG Audio
  
  
  
  Format version                           : Version 1
  
  
  
  Format profile                           : Layer 3
  
  
  
  Mode                                     : Joint stereo
  
  
  
  Mode extension                           : MS Stereo
  
  
  
  Codec ID                                 : 2
  
  
  
  Codec ID/Hint                            : MP3
  
  
  
  Duration                                 : 49hours
  
  
  
  Bit rate mode                            : CBR
  
  
  
  Bit rate                                 : 64.0 Kbps
  
  
  
  Channel(s)                               : 2 channels
  
  
  
  Sampling rate                            : 44.1 KHz
  
  
  
  Compression mode                         : Lossy
  
  
  
  Stream size                              : 13.3 GiB
  
  
  
  _____________________________________________________________________

  Because this is the flv piece generated from the Suse10.0 server, the timestamp may be not correctly wrote into the flv metadata. Therefore, the Duration item listed above is not the real time of it.
  I has record the time in its file name.
  So, the beginning time is 1775818137 ms
  the ending time of this flv is 1775828481 ms
  The actual duation of this flv is 10344 ms which is about 10 seconds.

  **HERE IS MY QUESTION -.- **

  When I use ffmpeg to transcode flv fromat into ts format, like this,

  ./ffmpeg -i 1775818137_1775828481_10344.flv -f mpegts -vn -acodec libfaac -ar 44100 -ab 48k 1775818137_1775828481_10344.ts

  Is there possibility that the duration of final gotten ts file is not equal to the duation of original flv file ? In other words, the ts file's duration is not 10344ms.

• Replacing the standard Android H264 software encoder with an ffmpeg based one

  10 août 2012, par rubenvb

  In Android ICS and later, a new OpenMax IL API version is in use, making old binary blobs useless/unused. This leads to older devices that otherwise run ICS just fine and dandy to have broken video playback (YouTube HQ and IMBD, for example) because Androids fallback software decoder sucks when compared to what ffmpeg can do on the same device (I tested MXPlayer+arm6vfp ffmpeg and a 720p movie played back great).

  I am trying to dig through the Android source code to see where and what exactly I could add/replace code to allow the ffmpeg library's awesomeness to be used. The problem is I don't know exactly what code is being used in for example the YouTube app to decode video, or how that's decided.

  So I have two options as far as I can tell :

  1. Figure out the current software decoder being used, and try to wrap its external interface around ffmpeg, effectively replacing the slow software decoder currently used. The end result would be a single .so I could push to the device.

  2. Figure out how to trick Android into thinking an OMX library based on ffmpeg (I have built one succesfully for Android : limoa) and add this somewhere to the list of considered libraries (or better : replace the unusable hardware codec).

  As an extension, I'd like to also make camcorder video encoding work through this, so a true integrated solution would be very much wanted. The question is : how, and where, and what ? Searching the Android source tree gives numerous counts of "H264" and related stuff in many different places. I need the lowest and simplest possible, so I can simply wrap the hypothetical decode(buffer) function call to use ffmpeg (libavcodec).