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Re: [Linphone-developers] rtp timestamp for video

From: Pramod Bhagwat
Subject: Re: [Linphone-developers] rtp timestamp for video
Date: Wed, 19 Dec 2007 12:42:36 +0530

Thanks Simon.  i made one more observation if i increment the user_ts value with 240 (like audio timestamp for 30 millisecond) then rtp_session_sendm_with_ts() function is taking 26 to 30 millisecond. Does this give any hint?
For streaming the video i have modified the rtpsend application present in the tests folder of the ortp. i have registered avprofile payload_type_h263_1998 and using payload 96 (dynamic).

Warm Regards,

On Dec 14, 2007 3:01 PM, Simon Morlat <address@hidden> wrote:

Usually cameras have approximate frames per second values. Incrementing the
timestamp by 90000/30 is not reliable.
You should instead do a gettimeofday each time the camera gives you a frame,
and then send the packet with a timestamp derived from the gettimeofday time.
uint32_t ts=(uint32_t) (current_time_in_milliseconds*90);


Le Monday 10 December 2007 13:44:37 Pramod Bhagwat, vous avez écrit:
> Hi,
> I am using oRTP to stream the video data from the camera on Linux. I am
> using H.263 codec  for sending the video data. I am using custom H.263
> codec and added the H.263 header packetization  routines using
> rtp_session_create_packet() function and then sending the data using
> rtp_session_sendm_with_ts() function.
> Here I am incrementing "user_ts" value by 3000 Since the Camera outputs 30
> frames per second.
> i.e. 90000/30 = 3000.
> But when i profiled the rtp_session_sendm_with_ts() function using
> gettimeofday it is taking 400 millisecond which is very large value.
> Is there any thing wrong in my timestamp calculation. Please let me know.
> Warm Regards,
> pramod

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