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• Encoding H.264 CBR videos with FFmpeg

  27 août 2015, par Cornstalks

  I’m trying to encode a video with ffmpeg into H.264 (via the libx264 library) with a constant bit rate. I know, I know, VBR is often preferred, but for this specific job I’m required to use CBR (just as long as it’s so many kilobytes per second ; it doesn’t have to be an exact kilobytes per frame, afaik). My sample video I’m using to test is from here : http://a1408.g.akamai.net/5/1408/1388/2005110403/1a1a1ad948be278cff2d96046ad90768d848b41947aa1986/sample_iTunes.mov.zip (it comes from http://support.apple.com/kb/HT1425)

  I can get a constant bit rate when encoding the video with MPEG-4 Video (using the commands ffmpeg -i sample_iTunes.mov -b 819968 -minrate 819968 -maxrate 819968 out.mov), and the bit rate is as expected. Reading the video’s specs via the QuickTime Inspector, it’s got a data rate of 844.94 kbit/s. Cool.

  However, when I change the codec to libx264, it seems to completely ignore my bitrate requests ! The command I’m trying is "ffmpeg -i sample_iTunes.mov -vcodec libx264 -vpre medium -b 819968 -vb 819968 -minrate 819968 -maxrate 819968 -bufsize 400000 test.mov". But when I check the video’s specs via the QuickTime Inspector, it’s got a data rate of 254.74 kbit/s. WTF ? That’s not even close !

  I’ve tried changing so many parameters and adding tons of different things, and I’ve spent 2 days googling this, but I can’t seem to get it to work. If I encode the video with the MainConcept H.264 encoder, I can get a constant bitrate, but I need this to work with ffmpeg.

  If someone can help me figure out how to do CBR H.264 encoding with FFmpeg, I will love you forever !

• Consume FFmpeg XCFramework from Objective-C, headers not found

  19 novembre 2020, par jamone

  I built FFmpeg for Apple's platforms as an XCFramework. I used the script in https://github.com/kewlbear/FFmpeg-iOS-build-script/pull/147 to do so.

  



  I'm trying to now consume that framework inside a traditional iOS/macOS framework (named VideoEditing), that then is used inside my iOS app (soon to try and be Catalyst).

  



  In VideoEditing I have linked to FFmpeg.xcframework and then in the app that uses VideoEditing I have linked & embedded FFmpeg.xcframework. Previously I was building FFmpeg as a standard static library, and using that from inside VideoEditing in a Objective-C++ wrapper so I can use it all from Swift.

  



  In that Objective-C++ file I would import FFmpeg headers like #import <libswscale></libswscale>swscale.h> To make that work, I had to set header search paths. How are you supposed to do it once you convert to the XCFramework ? I've tried @import FFmpeg, #import <ffmpeg></ffmpeg>libswscale/swscale.h>, #import <ffmpeg></ffmpeg>swscale.h> as well as #import <libswscale></libswscale>swscale.h>. In every case I just get a file not found error on the import line.

  



  All of Apple's examples are showing it just in Swift with the framework vending a module. If I was to try and still set a header search path, you now have different headers per architecture.

  



  

  


• What is the difference between yuv420p and yuv420p(tv) ?

  9 novembre 2018, par Aleksandr Shemetillo

  I am trying to implement Fairplay ready browser player (Apple’s DRM).
  A stream that has h264(Main) yuv420p(tv) settings becomes non-working after drm decryption (crashed picture of green color). Converting again the video with a "Main" ffmpeg profile changes the setting to a simple yuv420 and this solves the problem.
  Please explain the difference.
  Or maybe some other changes I don’t see can happen during the conversion ?

  Of course, since we are talking about Fairplay, the problem is observed in Safari on Os X