Newest 'x264' Questions - Stack Overflow

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• In FFmpeg, encoding anything lower than slow preset takes video to level 5

  1er septembre 2015, par Leo Zerino

  Why whenever I use any preset lower or equal to slow, it makes my video High@L5 (profile high / level 5)? It doesn't make sense to me, I always tought that levels were associeted with frame size, frame rate and data rate only

  I've searched all over for a relation between presets and levels in x264 encoding through FFmpeg, but couldn't find any.

  My only concern is compatibility, since anything above 4 tends to be exotic to most players.

• Is there a need to apply Deblocking filter, when I have all Intra frames Encoding

  31 août 2015, par Codec Guy

  I am working on H.264 Deblocking Filter and need some clarity.

  • While designing an all Intra Encoder and Decoder, is it mandatory to add Deblocking Filter block in the Codec.
  • If deblocking filter is not enabled for all Intra Encoding does that cause any PSNR degradation(I checked few streams the PSNR almost remained the same).
  • If I am encoding all my frames using Intra prediction, does that also have any blocking artifacts.

  Thanks in advance

• x264 library speed - Altivec vs SSE4 -

  15 août 2015, par Asain Kujovic

  I have simple cheap dualcore intel-3ghz-debian and access to super-expensive powerPc7-Aix.

  And after few days of strugle, i compiled libx264 and tested it on both computers:

  1. GCC: library x264 on intel (with SSE2 capabilities) and
  2. GCC on 16 core powerPc (with altivec).

  ... and result is that cheap intel is x2 times faster ! (with altivec disabled, intel is 10x times faster)

  My question: is this normal? Does all other powerPC-users have same results? Can powerPc-altivec-optimisation of x264 library work at same speed with intel... or MMX/SSE optimisation is officially at least 2 times faster for this library?

  I am not interested in multi-thread options. Number of cores and threads are irrelevant. Just simple one-thread x264 encoding with default "medium preset" using rawvideo as source, sse vs altivec.

  Maybe native Aix XLC compiler provide better results? (i managed only gcc to work)

  ... mac-powerpc-users maybe know something about this.

  powrPc7-Aix:$ time (cat raw10sec.y4m |x264 --input-res 720x576 --fps 50 -o /dev/null -)
  x264: 64-bit XCOFF
  x264 [info]: using cpu capabilities: Altivec
  time: real 0m33.559s
  ---
  intelDebian:$ time (cat raw10sec.y4m |x264 --input-res 720x576 --fps 50 -o /dev/null -)
  x264: ELF 32-bit LSB executable
  x264 [info]: using cpu capabilities: MMX2 SSE2Fast SSSE3 FastShuffle SSE4.1 Cache64
  time: real 0m16.503s
  

• decode a mp4 video with gstreamer

  12 août 2015, par KKc

  I want to play a mp4 video in Gstreamer, but i got an error with the x264dec which is not found. I wrote this pipeline

    gst-launch filesrc \
       location=/media/thesis/Gstreamer/pub_Irma.mp4 \
     ! qtdemux name=demux demux. ! queue ! faad \
     ! audioconvert ! audioresample ! autoaudiosink demuxer. \
     ! queue ! x264dec ! ffmpegcolorspace ! autovideosink 
  

  After this step, my aim is to generate execution traces of a mp4 video decoding. I don't know where is the problem with x264dec.

• libx264 : which parameters can be changed on fly ?

  11 août 2015, par Dan Tumaykin

  I know that it is possible to change some encoder parameters on fly, using x264_encoder_reconfig(). From this commit I can deduce that we can change ratecontrol parameters - but I was unable to find a clear list of parameters that may be changed.

  Question: which parameters of x264 encoder can be changed on fly?