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• problem : FFMPEG seeking with av_seek_frame using byte positions

  16 juillet 2012, par Nick Verlinden

  I am trying to get the av_seek_frame() function to go to a byte position I specify. I am implementing a frame accurate seeking mechanism for my application, and the way I see it, I will scan the entire video file, and store byte positions for each keyframe in a struct. I found out where to get the current byte position : AVPacket.pos. I now test this position with av_seek_frame like this :

  av_seek_frame( pFormatCtx, videoStream, 110285594, AVSEEK_FLAG_BYTE);

  However, this does not seem to do the right thing, when I call av_read_frame, it just starts with frame 23. If I do not seek, it starts at frame 1.

• Achieving very poor fps for my iphone app for decode + display h264 frames using ffmpeg and opengl

  29 décembre 2015, par sam18

  I have three steps process for my application which display h264 frame on iPhone screen.

  1. decode using ffmpeg.
  2. scale and colorspace conversion (scale to 256 X 256 Opengl ES 1 texture and convert colospace from yuv420p to rgb565 using sws_Scale from ffmpeg).
  3. Render opengl 1 texture to frame buffer to render buffer

  after these three step process, I got my picture on iPhone screen.

  When I was testing the performance for 720 X 576 resolution frames, I obtain very poor FPS. It is reaching max to 180 milliseconds and hence resulting into 5 to 6 FPS.

  Any direction will be grateful.

• Is Java fast enough to do live screensharing ?

  10 mars 2012, par user1260501

  For the past few months, a developer and I have been working on a screensharing applet that streams to a media server like Wowza or Red5, but no matter what we do, we have about 5 seconds of latency, which is too long for a live application where people are interacting with each other. We've tried xuggle, different encoders, different players, different networks, different media servers, and even streaming locally, there's significant latency.

  So, I'm beginning to wonder…

  Is Java fast enough to do live screensharing ?

  I've seen lots of screen recording applets written in Java, but none of them are streaming live. Everything that's done live, such as GoToMeeting, seems to use C++. I'm thinking maybe there's a reason.

  It's not a compression problem. Using ScreenVideo, we've compressed an hour-long stream down to about 100 MB, and we have plenty of bandwidth. The processor isn't overloaded doing the compression, either, but it seems to be taking too much time. We are getting the best results from some code pulled out of BigBlueButton, but still, the latency is terrible.

  Streaming the WebCam, on the other hand, is nice and snappy. Almost no latency at all. So, the problem is the applet.

  The only other idea I can think of is somehow emulating a WebCam with Java. Not sure if that would be faster or not.

  Ideas ? Or should I just give up on Java and do this in C++ ? I would hate to do that, because then I would have to create different versions for different platforms, but if it's the only way, it's the only way.