[vlc-devel] RTSP and PCM 48kHz

[Wiecaszek, Lukasz]

Hallo Guys,

We are using VLC as the client for RTSP transmission of PCM samples with 48000 Hz sampling rate.
Below you can find RTSP handshake. GStreamer is the RTSP server.
The biggest problem we are encountering is the value of timestamps inside the RTP packets.
GStreamer RTSP server produces timestamp values with the clock according to the audio sampling rate. So in our case it is 48kHz.
But with this settings VLC has problems with buffering incoming data.
Although type of incoming samples is recognized properly.
Also log is attached.

Stream: 0
Codek: PCM S16 BE (s16b)
Channels: Stereo
Samplig rate: 48000 Hz
Bits per sample: 16

Any hint, where is the problem would be appreciated. What is the clock frequency you are expecting the values in timestamp field are clocked?
RTP packet header

Bit offset[b]<http://en.wikipedia.org/wiki/Real-time_Transport_Protocol#cite_note-20>

0-1

2

3

4-7

8

9-15

16-31

0

Version

P

X

CC

M

PT

Sequence Number

32

Timestamp

64

SSRC identifier

96

CSRC identifiers
...

96+32×CC

Profile-specific extension header ID

Extension header length

128+32×CC

Extension header
...


OPTIONS rtsp://192.168.1.111:9554/radio RTSP/1.0
CSeq: 2
User-Agent: LibVLC/2.1.2 (LIVE555 Streaming Media v2013.12.05)

RTSP/1.0 200 OK
CSeq: 2
Public: OPTIONS, DESCRIBE, GET_PARAMETER, PAUSE, PLAY, SETUP, SET_PARAMETER, TEARDOWN
Server: GStreamer RTSP server
Date: Tue, 30 Sep 2014 22:03:02 GMT

DESCRIBE rtsp://192.168.1.111:9554/radio RTSP/1.0
CSeq: 3
User-Agent: LibVLC/2.1.2 (LIVE555 Streaming Media v2013.12.05)
Accept: application/sdp

RTSP/1.0 200 OK
CSeq: 3
Content-Type: application/sdp
Content-Base: rtsp://192.168.1.111:9554/radio/
Server: GStreamer RTSP server
Date: Tue, 30 Sep 2014 22:03:02 GMT
Content-Length: 278

v=0
o=- 1188340656180883 1 IN IP4 192.168.1.111
s=Session streamed with GStreamer
i=rtsp-server
t=0 0
a=tool:GStreamer
a=type:broadcast
a=control:*
a=range:npt=now-
m=audio 0 RTP/AVP 96
c=IN IP4 0.0.0.0
b=AS:1536
b=RR:0
a=rtpmap:96 L16/48000/2
a=control:stream=0
SETUP rtsp://192.168.1.111:9554/radio/stream=0 RTSP/1.0
CSeq: 4
User-Agent: LibVLC/2.1.2 (LIVE555 Streaming Media v2013.12.05)
Transport: RTP/AVP;unicast;client_port=61636-61637

RTSP/1.0 200 OK
CSeq: 4
Transport: RTP/AVP;unicast;client_port=61636-61637;server_port=52814-52815;ssrc=8B3F96E6;mode="PLAY"
Server: GStreamer RTSP server
Session: Mb%24baCis1QbCVosp
Date: Tue, 30 Sep 2014 22:03:02 GMT

PLAY rtsp://192.168.1.111:9554/radio/ RTSP/1.0
CSeq: 5
User-Agent: LibVLC/2.1.2 (LIVE555 Streaming Media v2013.12.05)
Session: Mb%24baCis1QbCVosp
Range: npt=0.000-

RTSP/1.0 200 OK
CSeq: 5
RTP-Info: url=rtsp://192.168.1.111:9554/radio/stream=0;seq=13945;rtptime=3642289100
Range: npt=now-
Server: GStreamer RTSP server
Session: Mb%24baCis1QbCVosp
Date: Tue, 30 Sep 2014 22:03:02 GMT

GET_PARAMETER rtsp://192.168.1.111:9554/radio/ RTSP/1.0
CSeq: 6
User-Agent: LibVLC/2.1.2 (LIVE555 Streaming Media v2013.12.05)
Session: Mb%24baCis1QbCVosp

RTSP/1.0 200 OK
CSeq: 6
Server: GStreamer RTSP server
Date: Tue, 30 Sep 2014 22:03:02 GMT
Serdecznie pozdrawiam / Kind Regards,
Lukasz Wiecaszek
Software Engineer
I&DI Reception Systems

Delphi, Technical Center Krakow
Poland, 30-399 Krakow, ul. Podgorki Tynieckie 2
Phone: [+48] 12 252 1701
E-mail: lukasz.wiecaszek at delphi.com<mailto:lukasz.wiecaszek at delphi.com>


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