[Live-devel] How to re transmit

[Jeff Shanab]

In the simplest case, H264 defines a protocol that starts with a key frame and has a succession of difference frames that are much smaller. ie the 24KByte key frame has all the information needed to draw the whole frame and the 1Kbyte diff frame has only the changes needed to update the key frame to the new display frame.
The first difference frame depends on the key frame and each diff frame depends on the key frame and the changes made by all the proceeding diff frames.

One trick would be to have a key frame per second and send and display only keyframes.
But since the keyframes are big you can expect at most a 60% reduction on 30fps video.

Anything else is transcoding. Decode the video at the source fps and re-encode at the fps you want to display.
This can be done in software with libavcodec, but it takes CPU!
This also would let you reduce the resolution, sometimes the client is not viewing it at full resolution and that effects bandwidth considerably.
________________________________
From: live-devel-bounces at ns.live555.com [live-devel-bounces at ns.live555.com] on behalf of Tarun Batra [tbatra18 at gmail.com]
Sent: Thursday, October 11, 2012 10:20 AM
To: live-devel at ns.live555.com
Subject: [Live-devel] How to re transmit

Hello Sir,

     I have implemented “testOnDemandRTSPServer” on my machine which receives h264 transport stream from my streamer application.

     Is there any way to re transmit this received stream from streamer, to my RTSP clients with different fame rates? As some of my RTSP clients do not have sufficient bandwidth to receive stream with high frame rate. My streamer uses MPEG1or2VideoStreamDiscreteFramer to stream a video from digital camera.

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