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• FFmpeg decoding H264

  25 septembre 2011, par Steve McFarlin

  I am decoding a H264 stream using FFmpeg on the iPhone. I know the H264 stream is valid and the SPS/PPS are correct as VLC, Quicktime, Flash all decode the stream properly. The issue I am having on the iPhone is best shown by this picture.

  

  It is as if the motion vectors are being drawn. This picture was snapped while there was a lot of motion in the image. If the scene is static then there are dots in the corners. This always occurs with predictive frames. The blocky colors are also an issue.

  I have tried various build settings for FFmpeg such as turning off optimizations, asm, neon, and many other combinations. Nothing seems to alter the behavior of the decoder. I have also tried the Works with HTML, Love and Peace releases, and also the latest GIT sources. Is there maybe a setting I am missing, or maybe I have inadvertently enabled some debug setting in the decoder.

  Edit

  I am using sws_scale to convert the image to RGBA. I have tried various different pixel formats with the same results.

  sws_scale(convertCtx, (const uint8_t**)srcFrame->data, srcFrame->linesize, 0, codecCtx->height, dstFrame->data, dstFrame->linesize);

  I am using PIX_FMT_YUV420P as the source format when setting up my codec context.

• Rotating videos with FFmpeg

  19 février 2016, par jocull

  I have been trying to figure out how to rotate videos with FFmpeg. I am working with iPhone videos taken in portrait mode. I know how to determine the current degrees of rotation using MediaInfo (excellent library, btw) but I’m stuck on FFmpeg now.

  From what I’ve read, what you need to use is a vfilter option. According to what I see, it should look like this :

  ffmpeg -vfilters "rotate=90" -i input.mp4 output.mp4

  However, I can’t get this to work. First, -vfilters doesn’t exist anymore, it’s now just -vf. Second, I get this error :

  No such filter: 'rotate'
  
  Error opening filters!

  As far as I know, I have an all-options-on build of FFmpeg. Running ffmpeg -filters shows this :

  Filters:
  
  anull            Pass the source unchanged to the output.
  
  aspect           Set the frame aspect ratio.
  
  crop             Crop the input video to x:y:width:height.
  
  fifo             Buffer input images and send them when they are requested.
  
  format           Convert the input video to one of the specified pixel formats.
  
  hflip            Horizontally flip the input video.
  
  noformat         Force libavfilter not to use any of the specified pixel formats
  
   for the input to the next filter.
  
  null             Pass the source unchanged to the output.
  
  pad              Pad input image to width:height[:x:y[:color]] (default x and y:
  
   0, default color: black).
  
  pixdesctest      Test pixel format definitions.
  
  pixelaspect      Set the pixel aspect ratio.
  
  scale            Scale the input video to width:height size and/or convert the i
  
  mage format.
  
  slicify          Pass the images of input video on to next video filter as multi
  
  ple slices.
  
  unsharp          Sharpen or blur the input video.
  
  vflip            Flip the input video vertically.
  
  buffer           Buffer video frames, and make them accessible to the filterchai
  
  n.
  
  color            Provide an uniformly colored input, syntax is: [color[:size[:ra
  
  te]]]
  
  nullsrc          Null video source, never return images.
  
  nullsink         Do absolutely nothing with the input video.

  Having the options for vflip and hflip are great and all, but they just won’t get me where I need to go. I need to the ability to rotate videos 90 degrees at the very least. 270 degrees would be an excellent option to have as well. Where have the rotate options gone ?

• encoding using ffmpeg for mac app

  9 mai 2012, par user946061

  In my mac app i am using ffmpeg library for video encoding in 4 different types of formats for iPhone, iPod, AppleTV and HD.But the encoding takes so much time and the CPU usage becomes very low.I want someone to get me any idea to maximize this CPU usage and minimize the encoding time-period so that the application may enhance the performance level.