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• armv6 : Accelerate ff_imdct_half for general case (mdct_bits != 6)

  11 juillet 2014, par Ben Avison

  armv6 : Accelerate ff_imdct_half for general case (mdct_bits != 6)
  The previous implementation targeted DTS Coherent Acoustics, which only
  
  requires mdct_bits == 6. This relatively small size lent itself to
  
  unrolling the loops a small number of times, and encoding offsets
  
  calculated at assembly time within the load/store instructions of each
  
  iteration.
  In the more general case (codecs such as AAC and AC3) much larger arrays
  
  are used - mdct_bits == [8, 9, 11]. The old method does not scale for
  
  these cases, so more integer registers are used with non-unrolled versions
  
  of the loops (and with some stack spillage). The postrotation filter loop
  
  is still unrolled by a factor of 2 to permit the double-buffering of some
  
  VFP registers to facilitate overlap of neighbouring iterations.
  I benchmarked the result by measuring the number of gperftools samples
  
  that hit anywhere in the AAC decoder (starting from aac_decode_frame())
  
  or specifically in ff_imdct_half_c / ff_imdct_half_vfp, for the same
  
  example AAC stream :
                    Before          After
  
                    Mean   StdDev   Mean   StdDev  Confidence  Change
  
  aac_decode_frame  2368.1 35.8     2117.2 35.3    100.0%      +11.8%
  
  ff_imdct_half_*   457.5  22.4     251.2  16.2    100.0%      +82.1%
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavcodec/arm/mdct_vfp.S

• doc/ffserver : move general stream options upwards in the list

  28 novembre 2013, par Stefano Sabatini

  doc/ffserver : move general stream options upwards in the list
  

  • [DH] doc/ffserver.texi

• FFMPEG Stream series of pictures over network

  11 septembre 2015, par Commodore63

  I would like to generate video frames on one computer and stream them to another computer to be manipulated and displayed. I want to do this programatically, because the source images are generated from a 3rd party c++ library and on the receiving end I want to manipulate the images before displaying them. I have been pulling my hair out trying FFMPEG. I got the encoding example to work, but am not sure what to do after that. I have just about googled everything i could think of but cannot figure out which FFMPEG library/function to call once I have a stuffed AVPacket. It seems that I need to use either the AVIO or AVFormat or the muxer but it is not clear how to initialize and get them working. I would appreciate any help you could offer.

  To provide some context I have the example ’decoding_encoding.c’ which is provided with ffmpeg working. Here is the spot that I am struggling with :

          /* encode the image */
  
          ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
  
          if (ret < 0) {
  
              fprintf(stderr, "Error encoding frame\n");
  
              exit(1);
  
          }
  
  
  
          if (got_output) {
  
              printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
              fwrite(pkt.data, 1, pkt.size, f);
  
  
  
              //
  
              // instead of writing to a file, i want to stream to a network
  
              // What do I need to do with pkt to do that?
  
              //
  
              av_free_packet(&pkt);
  
          }

  Most documentation (and the Dranger tutorial) focus on reading and writing files. I do not need to use a file. I want to stream video over a network. It seems like I need AVFormat and AVio but I jsut can’t figure out how they fit together.