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• How Much H.264 In Each Encoder ?

  8 septembre 2010, par Multimedia Mike — General

  Thanks to my recent experiments with code coverage tools, I have a powerful new — admittedly somewhat specious — method of comparing programs. For example, I am certain that I have read on more than one occasion that Apple’s H.264 encoder sucks compared to x264 due, at least in part, to the Apple encoder’s alleged inability to exercise all of H.264′s features. I wonder how to test that claim ?

  Experiment
  Use code coverage tools to determine which H.264 encoder uses the most features.

  Assumptions

  • Movie trailers hosted by Apple will all be encoded with the same settings using Apple’s encoder.
  • Similarly, Yahoo’s movie trailers will be encoded with consistent settings using an unknown encoder.
  • Encoding a video using FFmpeg’s libx264-slow setting will necessarily throw a bunch of H.264′s features into the mix (I really don’t think this assumption holds much water, but I also don’t know what “standard” x264 settings are).

  Methodology

  • Grab a random Apple-hosted 1080p movie trailer and random Yahoo-hosted 1080p movie trailer from Dave’s Trailer Page.
  • Use libx264/FFmpeg with the ‘slow’ preset to encode Big Buck Bunny 1080p from raw PNG files.
  • Build FFmpeg with code coverage enabled.
  • Decode each file to raw YUV, ignore audio decoding, generate code coverage statistics using gcovr, reset stats after each run by deleting *.gcda files.

  Results

  • x264 1080p video : 9968 / 134203 lines
  • Apple 1080p trailer : 9968 / 134203 lines
  • Yahoo 1080p trailer : 9914 / 134203 lines

  I also ran this old x264-encoded file (ImperishableNightStage6Low.mp4) through the same test. It demonstrated the most code coverage with 10671 / 134203 lines.

  Conclusions
  Conclusions ? Ha ! Go ahead and jump all over this test. I’m already fairly confident that it’s impossible (or maybe just very difficult) to build a single H.264-encoded video that exercises every feature that FFmpeg’s decoder supports. For example, is it possible for a file to use both CABAC and CAVLC entropy methods ? If it’s possible, does any current encoder do that ?

• vulkan_av1 : port to the new stable API

  19 janvier 2024, par Lynne

  vulkan_av1 : port to the new stable API
  Co-Authored-by : Dave Airlie <airlied@redhat.com>
  

  • [DH] configure
  • [DH] libavcodec/Makefile
  • [DH] libavcodec/vulkan_av1.c
  • [DH] libavcodec/vulkan_decode.c
  • [DH] libavcodec/vulkan_decode.h
  • [DH] libavcodec/vulkan_video.h
  • [DH] libavcodec/vulkan_video_codec_av1std_decode_mesa.h
  • [DH] libavcodec/vulkan_video_codec_av1std_mesa.h
  • [DH] libavutil/hwcontext_vulkan.c
  • [DH] libavutil/vulkan_functions.h
  • [DH] libavutil/vulkan_loader.h

• Live video encoding using...?

  27 décembre 2013, par Basic

  I'm attempting to write a fairly simplistic application that will stream video/audio from a webcam to someone else across the internet (ala Skypebut with more control).

  There seems to be very little useful/relevant information on the subjectand what I can find is largely outdated. From my research so far, x264 seems to be the way to go as it offers an ultrafast option which is designed for this situation

  I'm able to turn on the webcam and receive a stream of images. I can also listen on an audio device and get samples.

  Where I'm failing is encoding that information in such a way as to be able to stream with a minimum of latency (from what I've read, 200ms delay is the goal for no obvious lag, including network latency - so let's aim for 100-150ms)

  Things I've tried

  ffmpeg

  This seems to be the most widely used option for encoding. I've had two real issues using it. Firstly, even using x264 with no look-aheads and the bare minimum buffers for stability, the delay seems to be on the order of 700ms using image2pipe. Secondly, it requires ffmpeg to be installed - being able to do this without an external dependency would be nice.

  VLC

  As with ffmpeg this requires an external program which is a negative. Even worse, I can't seem to get a latency of under 2 seconds which seems to increase over time. I've also only been able to get VLC to capture the camera itself rather than take a stream of images which means I don't get a chance to pre-process them.

  DirectShow

  I've seen a number of sites recommending using the windows direct show encoders but I haven't been able to find one that works at anything like real time. In fact, the only one I've managed to get going reliably is a Windows Media codec that has a massive latency and fairly large size.

  Other considerations

  None of the above address the problem of adding an audio stream to the video. I'm not sure if I should attempt to encode them together or send a separate stream alongside the video.

  In short, I've been Googling for a week or so now and haven't found a decent way to do this. Can someone please point me at a decent example/guide ?