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• avcodec/asvenc : Avoid reversing output data twice

  13 octobre 2020, par Andreas Rheinhardt

  avcodec/asvenc : Avoid reversing output data twice
  The ASUS V2 format is designed for a little-endian bitstream reader, yet
  
  our encoder used an ordinary big-endian bitstream writer to write it ;
  
  the bits of every byte were swapped at the end and some data (namely the
  
  numbers not in static tables) had to be bitreversed before writing it at
  
  all, so that it would be reversed twice.
  This commit stops doing so ; instead, a little-endian bitstream writer is
  
  used. This also necessitated to switch certain static tables, which
  
  required trivial modifications to the decoder (that uses the same
  
  tables).
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/asv.c
  • [DH] libavcodec/asv.h
  • [DH] libavcodec/asvdec.c
  • [DH] libavcodec/asvenc.c

• Python Send stdout and stderr to Multiple files using stored in Variable

  17 avril 2021, par D0n

  Here is my scripts

  


  csv_location = '/home/scripts/streams.csv'
ffmpeg_location = '/usr/bin/ffmpeg'
ffmpeglogs = '/home/scripts/ffmpeglog/'

# Open the streams list csv file
with open(csv_location) as csv_file:
    csv_reader = csv.reader(csv_file, delimiter=',')
    for row in csv_reader:
        ffmpeg_log = (ffmpeglogs + row[0]) # set the ffmpeg log to be named the stream name
        # Open log file for writing
        with open(ffmpeg_log, 'wb') as ffmpeg_output: 
            # Iterate through streams list
            for row in csv_reader:
                print(row)
                stream_output = (row[0] + ".mpeg") # stream output variable
                # Subprocess record 1 stream at a time & send the output t0 stdout & stdeer
                ffmpeg_instance = subprocess.Popen([ffmpeg_location, '-t', '10', '-i', row[1], stream_output], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
                # sent output to ffmpeg log
                ffmpeg_output.write(ffmpeg_instance.communicate()[1])


  


  Here is my CSV File

  


  Name,RTSP_URL
stream1,rtsp://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mov
stream3,rtsp://wowz.streamlock.net/vod/mp4:BigBuckBunny_115k.mov
stream4,rtsp://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mov


  


  So I have a script that reads a CSV file and ffmpeg records the video for 10 seconds. Then spits the output of the FFMPEG to a file. I need each camera to have its own file. Really just to log FFMPEG output for each camera. But my issue is that the FFMPEG output for multiple cameras get written to 1 file.

  


  Here is what I want to see in /home/scripts/ffmpeglog/

  


  stream1 stream3 stream4


  


  Here's what I'm actually what I see in /home/scripts/ffmpeglog/

  


  name stream1


  


• The First Problem

  19 janvier 2011, par Multimedia Mike — HTML5

  A few years ago, The Linux Hater made the following poignant observation regarding Linux driver support :

  Drivers are only just the beginning... But for some reason y’all like to focus on the drivers. You know why lusers do that ? Because it just happens to be the problem that people notice first.

  And so it is with the HTML5 video codec debate, re-invigorated in the past week by Google’s announcement of dropping native H.264 support in their own HTML5 video tag implementation. As I read up on the fiery debate, I kept wondering why people are so obsessed with this issue. Then I remembered the Linux Hater’s post and realized that the video codec issue is simply the first problem that most people notice regarding HTML5 video.

  I appreciate that the video codec debate has prompted Niedermayer to post on his blog once more. Otherwise, I’m just munching popcorn on the sidelines, amused and mildly relieved that the various factions are vociferously attacking each other rather than that little project I help with at work.

  Getting back to the "first problem" aspect— there’s so much emphasis on the video codec ; I wonder why no one ever, ever mentions word one about an audio codec. AAC is typically the codec that pairs with H.264 in the MPEG stack. Dark Shikari once mentioned that "AAC’s licensing terms are exponentially more onerous than H.264′s. If Google didn’t want to use H.264, they would sure as hell not want to use AAC." Most people are probably using "H.264" to refer to the entire MPEG/H.264/AAC stack, even if they probably don’t understand what all of those pieces mean.

  Anyway, The Linux Hater’s driver piece continues :

  Once y’all have drivers, the fight will move to the next layer up. And like I said, it’s a lot harder at that layer.

  A few months ago, when I wanted to post the WebM output of my new VP8 encoder and thought it would be a nice touch to deliver it via a video tag, I ignored the video codec problem (just encoded a VP8/WebM file) only to immediately discover a problem at a different layer— specifically, embedding a file using a video tag triggers a full file download when the page is loaded, which is unacceptable from end user and web hosting perspectives. This is a known issue but doesn’t get as much attention, I guess because there are bigger problems to solve first (c.f. video codec issue).

  For other issues, check out the YouTube blog’s HTML5 post or Hulu’s post that also commented on HTML5. Issues such as video streaming flexibility, content protection, fullscreen video, webcam/microphone input, and numerous others are rarely mentioned in the debates. Only "video codec" is of paramount importance.

  But I’m lending too much weight to the cacophony of a largely uninformed internet debate. Realistically, I know there are many talented engineers down in the trenches working to solve at least some of these problems. To tie this in with the Linux driver example, I’m consistently stunned these days regarding how simple it is to get Linux working on a new computer— most commodity consumer hardware really does just work right out of the box. Maybe one day, we’ll wake up and find that HTML5 video has advanced to the point that it solves all of the relevant problems to make it the simple and obvious choice for delivering web video in nearly all situations.

  It won’t be this year.