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• Does 'keyint infinite' improve overall compression with crf and mb-tree ?

  23 avril 2012, par HitomiTenshi

  After reading what intra-refresh does, I kinda got confused. I'm encoding for YouTube and YouTube will re-encode the video-file anyways, so I thought "why not removing all these heavy IDR-frames ?" I just want to compress my video as hard as possible, enabling everything that could help me getting a lower filesize, but still maintaining a high quality.

  I used to test around stuff with lossless QP encoding, but the only thing I could max out was the merange. Here is a paste of my x264 settings : Pastebin.

  I want to achieve highest compression while maintaining visually lossless quality. (using crf values around 10 - 13, and merange 32)

  Could anyone give me advice on how to compress my video super hard (without touching the crf value !). I also want to know if it's true, that keyint infinite reduces overall compression.

• FFmpeg does not decode h264 stream

  5 juillet 2012, par HAPPY_TIGER

  I am trying to decode h264 stream from rtsp server and render it on iPhone.

  I found some libraries and read some articles about it.

  Libraries are from dropCam for iPhone called RTSPClient and DecoderWrapper.

  But I can not decode frame data with DecodeWrapper that using on ffmpeg.

  Here are my code.

  VideoViewer.m
  
  
  
  - (void)didReceiveFrame:(NSData*)frameData presentationTime:(NSDate*)presentationTime
  
  {
  
      [VideoDecoder staticInitialize];
  
      mConverter = [[VideoDecoder alloc] initWithCodec:kVCT_H264 colorSpace:kVCS_RGBA32 width:320 height:240 privateData:nil];
  
  
  
  
  
      [mConverter decodeFrame:frameData];
  
  
  
      if ([mConverter isFrameReady]) {
  
          UIImage *imageData =[mConverter getDecodedFrame];
  
          if (imageData) {
  
              [mVideoView setImage:imageData];
  
              NSLog(@"decoded!");
  
          }
  
      }
  
  }
  
  
  
  ---VideoDecoder.m---
  
  - (id)initWithCodec:(enum VideoCodecType)codecType 
  
           colorSpace:(enum VideoColorSpace)colorSpace 
  
                width:(int)width 
  
               height:(int)height 
  
          privateData:(NSData*)privateData {
  
      if(self = [super init]) {
  
  
  
          codec = avcodec_find_decoder(CODEC_ID_H264);
  
          codecCtx = avcodec_alloc_context();
  
  
  
          // Note: for H.264 RTSP streams, the width and height are usually not specified (width and height are 0).  
  
          // These fields will become filled in once the first frame is decoded and the SPS is processed.
  
          codecCtx->width = width;
  
          codecCtx->height = height;
  
  
  
          codecCtx->extradata = av_malloc([privateData length]);
  
          codecCtx->extradata_size = [privateData length];
  
          [privateData getBytes:codecCtx->extradata length:codecCtx->extradata_size];
  
          codecCtx->pix_fmt = PIX_FMT_RGBA;
  
  #ifdef SHOW_DEBUG_MV
  
          codecCtx->debug_mv = 0xFF;
  
  #endif
  
  
  
          srcFrame = avcodec_alloc_frame();
  
          dstFrame = avcodec_alloc_frame();
  
  
  
          int res = avcodec_open(codecCtx, codec);
  
          if (res < 0)
  
          {
  
              NSLog(@"Failed to initialize decoder");
  
          }
  
  
  
      }
  
  
  
      return self;    
  
  }
  
  
  
  - (void)decodeFrame:(NSData*)frameData {
  
  
  
  
  
      AVPacket packet = {0};
  
      packet.data = (uint8_t*)[frameData bytes];
  
      packet.size = [frameData length];
  
  
  
      int frameFinished=0;
  
      NSLog(@"Packet size===>%d",packet.size);
  
      // Is this a packet from the video stream?
  
      if(packet.stream_index==0)
  
      {
  
          int res = avcodec_decode_video2(codecCtx, srcFrame, &frameFinished, &packet);
  
          NSLog(@"Res value===>%d",res);
  
          NSLog(@"frame data===>%d",(int)srcFrame->data);
  
          if (res < 0)
  
          {
  
              NSLog(@"Failed to decode frame");
  
          }
  
      }
  
      else 
  
      {
  
          NSLog(@"No video stream found");
  
      }
  
  
  
  
  
      // Need to delay initializing the output buffers because we don't know the dimensions until we decode the first frame.
  
      if (!outputInit) {
  
          if (codecCtx->width > 0 && codecCtx->height > 0) {
  
  #ifdef _DEBUG
  
              NSLog(@"Initializing decoder with frame size of: %dx%d", codecCtx->width, codecCtx->height);
  
  #endif
  
  
  
              outputBufLen = avpicture_get_size(PIX_FMT_RGBA, codecCtx->width, codecCtx->height);
  
              outputBuf = av_malloc(outputBufLen);
  
  
  
              avpicture_fill((AVPicture*)dstFrame, outputBuf, PIX_FMT_RGBA, codecCtx->width, codecCtx->height);
  
  
  
              convertCtx = sws_getContext(codecCtx->width, codecCtx->height, codecCtx->pix_fmt,  codecCtx->width, 
  
                                          codecCtx->height, PIX_FMT_RGBA, SWS_FAST_BILINEAR, NULL, NULL, NULL); 
  
  
  
              outputInit = YES;
  
              frameFinished=1;
  
          }
  
          else {
  
              NSLog(@"Could not get video output dimensions");
  
          }
  
      }
  
  
  
      if (frameFinished)
  
          frameReady = YES;
  
  
  
  }

  The console shows me as follows.

  2011-05-16 20:16:04.223 RTSPTest1[41226:207] Packet size===>359
  
  [h264 @ 0x5815c00] no frame!
  
  2011-05-16 20:16:04.223 RTSPTest1[41226:207] Res value===>-1
  
  2011-05-16 20:16:04.224 RTSPTest1[41226:207] frame data===>101791200
  
  2011-05-16 20:16:04.224 RTSPTest1[41226:207] Failed to decode frame
  
  2011-05-16 20:16:04.225 RTSPTest1[41226:207] decoded!
  
  2011-05-16 20:16:04.226 RTSPTest1[41226:207] Packet size===>424
  
  [h264 @ 0x5017c00] no frame!
  
  2011-05-16 20:16:04.226 RTSPTest1[41226:207] Res value===>-1
  
  2011-05-16 20:16:04.227 RTSPTest1[41226:207] frame data===>81002704
  
  2011-05-16 20:16:04.227 RTSPTest1[41226:207] Failed to decode frame
  
  2011-05-16 20:16:04.228 RTSPTest1[41226:207] decoded!
  
  2011-05-16 20:16:04.229 RTSPTest1[41226:207] Packet size===>424
  
  [h264 @ 0x581d000] no frame!
  
  2011-05-16 20:16:04.229 RTSPTest1[41226:207] Res value===>-1
  
  2011-05-16 20:16:04.230 RTSPTest1[41226:207] frame data===>101791616
  
  2011-05-16 20:16:04.230 RTSPTest1[41226:207] Failed to decode frame
  
  2011-05-16 20:16:04.231 RTSPTest1[41226:207] decoded!
  
  . . . .  .

  But the simulator shows nothing.

  What's wrong with my code.

  Help me solve this problem.

  Thanks for your answers.

• Is it possible to force I_PCM mode in x264 ?

  10 octobre 2012, par cloudraven

  I need to use I_PCM mode in all blocks for some of I frames in video being compressed using x264. I know those frames will take a huge amount of space, but it is a requirement to keep them as faithful to the source as possible and to make them very fast to encode / decode (I_PCM should be super fast and lossless). Is there a way to force x264 to programatically do this.
  I am using libx264 to do this, but I haven't found a way to specify custom macroblock type within a given frame. If it is not supported, how hard would it be to modify the library to do so and where should I look at first ?