The VideoLAN Forums

Hi,

I have one question about using VLC as a client to receive AAC audio
from a server which is mulitcasting the audio stream. I got the SDP file
but I cannot use this file to receive the streaming audio(multicast), however, I can use QT to receive the audio stream through this SDP file.
So I am wondering whether VLC support openning the SDP file.
Thanks in advanced.

Paul

Hi,

I have one question about using VLC as a client to receive AAC audio
from a server which is mulitcasting the audio stream. I got the SDP file
but I cannot use this file to receive the streaming audio(multicast), however, I can use QT to receive the audio stream through this SDP file.
So I am wondering whether VLC support openning the SDP file.
Thanks in advanced.

Paul

Hmm! SDP?

1. Session Description Protocol (SDP) as in SDP/RTSP key management protocol identifiers?

2. Society of Decorative Painters (SDP)?

3. Streaming Download Project - SDP A Replacement of the MMS protocol?

4. Singapore Democratic Party (SDP)

As you can see I hate acronyms! If your answer is 2-4 we are all in trouble, as I can safely say NO.

However, If your answer is 1 you must understand what it is.

A session description expressed in SDP is a short structured textual description of the name and purpose of the session, and the media, protocols, codec formats, timing and transport information that are required to decide whether a session is likely to be of interest and to know how to start media tools to participate in the session.

SDP is purely a format for session description - it does not incorporate a transport protocol, and is intended to use different transport protocols as appropriate, including the Session Announcement Protocol.


RTSP is relatively new and I believe you would have better luck in Feature Requests.

Perhaps one of the Developers may have a better answer for you.

Put the SDP file online, so we can take a look please.

Put the SDP file online, so we can take a look please.

Thank you, DJ.

At first, I am sorry that I did not put my question in a proper way, since
I am just a newbie to SDP ( Session Description Procotol as you mentioned answer 1) I am trying to implement it according to my understand of the specification and use it to receive a multicast stream.


Following is the SDP file I wrote:

v=0;
o=IN IP4 192.168.0.137
i=radio3_fm.aac
t=0 0
a=type:broadcast
m=audio 16666 RTP/AVP 96
c=IN IP4 232.13.27.232/255
a=rtpmap:96 MPEG4-GENERIC/90000
a=fmtp:96 streamtype=5;profile-level-id=1;mode=AAC-hbr;sizelength=13;indexlength=3;indexdeltalength=3;config=1188

I tried this file by VLC and QT, I got warning from VLC that the data is garbage data, however, QT can receive the audio normally. I think maybe I need put more information in the SDP file so that the VLC can understand the receiving data and can decode them correctly since the QT can play it .

I am not sure what kind of information I shoud add or is there any information which is not right for VLC, so it just takes them as garbage?

Maybe I did not understand the protocol correctly, anyway, thanks for your kind help!

PS: the original AAC file which is streamed can be playback correctly by VLC.

v=0;

it should be v=0
not v=0;

v=0;

it should be v=0
not v=0;

Thank you for your answer. I am sorry for my careless.

However, VLC can still not decode the audio data correctly after
I modified that problem you mentioned. I am wondering that VLC
need mor information in the SDP file to know the format of the
data from the following message I got:

mod warning: MOD module discarded (path=@232.22.62.104:16666)
nsv warning: NSV module discarded
playlist warning: old import module discarded: invalid file
playlist warning: pls import module discarded
pva warning: PVA module discarded
ts warning: TS module discarded
ffmpeg debug: couldn't guess format
ps warning: this does not look like an MPEG PS stream, continuing anyway
main debug: using demux2 module "ps"
main debug: `rtp://@232.22.62.104:16666' sucessfully opened
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input
ps warning: garbage at input

Thanks for your reply.

The file should be opened by the liveMedia module.... apperently it isn't. Can you please provide FULL debug messages ?

The file should be opened by the liveMedia module.... apperently it isn't. Can you please provide FULL debug messages ?

Hi, DJ,

In fact, I almost printed out all the debug message from the message windows. After the initial information just as I gave to you, later it keeps on printing "Garbage at input". For me it seems that VLC got all the right audio frame, but it could not decode correctly since it did not know all the information from this SDP file. I am just guessing based on the fact that QT can decode it correctly. So I don't know what extra information I should put in the file to help VLC know more about the audio data.

Thanks a lot

The file should be opened by the liveMedia module.... apperently it isn't. Can you please provide FULL debug messages ?

Sorry, I am wondering is there any possibility that VLC did not call the right module to decode the audio data at this situation, since the message said: ps_warning. For me, it seems that VLC took these audio data as mpeg-2 program stream data, not AAC, so it can not decode it correctly.
Is this possible?

The file should be opened by the liveMedia module.... apperently it isn't. Can you please provide FULL debug messages ?

Hi, the DJ,

Can you give me some idea? Thank you very much.