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• Using Qt Media Player on Raspberry Pi 1

  18 mai 2015, par Mauker

  I have a project built using Qt5 which has to play a video. Just like in the videowidget sample code.

  I’ve followed these instructions to build qt5 on my Pi. And it went just fine. But when I try to run any qt program that uses QMediaPlayer, I get the error message :

  defaultServiceProvider::requestService(): no service found for - "org.qt-project.qt.mediaplayer"

  Which means I don’t have a backend to play the video, right ? Is there any one that I can use which will with Qt, like ffmpeg ? And how can I get it to work ? Specially for h264 videos.

  I’ve tried to install gstreamer as is told on this link, but it’s not working. Will I have to rebuild the entire qt5 again ?

  P.S. : I have the raspberry pi 1 model B with raspbian installed.

  Edit : As mentioned by Greenflow, I checked the ./configure log and saw that the GStreamer was compiled in, but the video apps are still not working...

  The message on the log was like this :

  GStreamer .............. yes (0.10)

  And the message on Greenflow’s log was like this :

  GStreamer .............. yes (1.0)

  Clearly it’s another version of GStreamer, but is it the problem ?

  I’ve also found this post which says QtMultimedia on the Pi is rather useless, but the post is from 2013, so I’m not sure if it’s really relevant. I’d like to have this app playing hardware accelerated videos on my Raspberry Pi, but I’m almost dropping the idea.

  Anyways, thanks Greenflow for the head start.

  Edit 2 : Found this thread on the Qtcentre. Damn, this thing is not going to be easy to solve, I guess...

• avcodec/mpeg_er : Simplify disabling IDCT

  13 juin 2024, par Andreas Rheinhardt

  avcodec/mpeg_er : Simplify disabling IDCT
  The error resilience code does not make up block coefficients
  
  and therefore zeroes them in order to disable the IDCT.
  
  But this can be done in a simpler manner, namely by setting
  
  block_last_index to a negative value. Doing so also has
  
  the advantage that the dct_unquantize functions are never even
  
  called for those codecs that do not use ff_mpv_reconstruct_mb()
  
  for ordinary decoding (namely RV-30/40 and the VC-1 family).
  This approach would not work for intra macroblocks (there is always
  
  at least one coefficient for them and therefore there is no check
  
  for block_last_index for them), but this does not happen at all.
  
  Add an assert for this.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/mpeg_er.c

• ffmpeg webcam capture a/v out of sync

  7 juillet 2014, par Cameron Ball

  I’m running this command to capture video and audio from my webcam :

  ffmpeg -y -f video4linux2 -s 320x240 -i /dev/video0 -f alsa -i "plughw:CARD=U0x46d0x825,DEV=0" -ac 2 -strict experimental Filename.mp4

  It works, but the audio is about half a second behind the video (EG if I clap, when I watch the video I’ll hear the clap and then see me do it).

  This is for an online stream, so I can’t fix it up later, it needs to be recorded correctly.

  It always seems to be off by the same amount, so I’m trying to find an option to simply delay when audio starts recording, but I can’t figure it out.

  Any ideas ?