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• 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).

• How can I change a video frame rate with FFmpeg, lossless and keeping the same total number of frames ?

  28 novembre 2019, par Nuno

  I’ve been searching for an answer here on Stack Overflow and googling everywhere... even though it seems like it should be a very simple command line to me, I just can’t find an answer anywhere.

  I would like to change the frame rate of a video from 23.976fps to 24fps with FFmpeg, lossless and keeping the total number of frames.

  To make it simpler :

  Let’s say I have a 25fps video with a total lenght of 100 frames.

  How can I change it’s frame rate to 50fps, with FFmpeg, lossless and keeping the same total lenght of 100 frames ?

  This was so far the best solution I came across with (which can be found here) :

  Extract the frames as rawvideo :

  ffmpeg -i input.mov -f rawvideo -b 50000000 -pix_fmt yuv420p -vcodec
  rawvideo -s 1920x1080 -y temp.raw

  Recreate the video with new framerate :

  ffmpeg -f rawvideo -b 50000000 -pix_fmt yuv420p -r 24 -s 1920x1080 -i
  temp.raw -y output.mov

  Note 1 : I had to remove "-b 50000000" when recreating the video with the new frame rate, in order to get it to work properly.

  It did exactly what I intended it to do, but I’m still wondering if there is any simpler way to do this ? I’ve tried to pipe them together in one line only, as suggested in the same post, but couldn’t get it to work.

  Note 2 : Even though it does exactly what I wanted it to do, I’ve just later realized there is quality loss using this method, which I would prefer to avoid.

  Thanks everyone in advance !

• Invalid Timestamps MPEG-TS - Nexio Server Errors

  25 octobre 2022, par Cody Greene

  I am trying to copy SAP audio from a 4ch MPEG-TS file to create an 8ch MPEG-TS file to help out a TV station partner that's struggling to do it on their own, but also running into problems.

  


  This pass copies ch 1-4 to 5-8

  


  


  ffmpeg -i input.ts -map 0:v -c:v copy -map 0:a -c:a copy -map 0:a -c:a copy firstpass.ts

  


  


  This pass mutes 3-6 (they wanted to "move" ch3-4 to ch7-8 and silence on 3-6) :

  


  


  ffmpeg -i firstpass.ts -map 0:v -c:v copy -map 0:a -filter:a:1 "volume=0" -filter:a:2 "volume=0" -c:a aac -b:a 128k output.ts

  


  


  The problem is that the Nexio is rejecting it for invalid timestamps, and copyts or flagging to genpts and gendts doesn't seem to work.

  


  It's fine with the source if I don't re-encode audio, and it's fine if I re-encode both video and audio (which we do not want to re-encode the video at all costs).

  


  Anyone got any ideas ?

  


  FFmpeg error :

  


  


  [mpegts @ 0x7fcadd204200] Invalid timestamps stream=0, pts=10714614, dts=10720620, size=3646

  


  


  Nexio error :

  


  


  [12:00:13] [33352 M] [XXXXX DISCONTINUITY : currentVideoFrameInfo.start = 631109472, expectedVideoFrameStart = 624238608]
[12:00:13] [33352 M] [XXXXX SMALL DISCONTINUITY. NOT CORRECTING TIME BASE HERE]
[12:00:13] [33352 M] [Error : PTL Error : discontinuous time stamp is detected. Actual lxf packet start = 630053424 (frame number = 26226). Expected lxf packet start = 623182560 (frame number = 25940)]
[12:00:13] [33352 M] [Error : PTL Error : processing is aborted (AbortImportIfMissingPacket = 1)]