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Decoding Dynamic Payloads.

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Do all RTP dynamic payloads are decoded or dissected as H.264??? If not, then what's the correct procedure.?? If yes, then it means all dynamic payload must contain video stream in it, but it isn't there in real. So plz make me understand that how to listen H.264. And also how to know that whether an RTP stream is carrying video or audio? I'm so confused in this regard. Although I'm in my learning stage. And learning gradually. I have successfully dissected Rtypayload 97 to H.264. But there whatever when I analysed that stream and tried to play it using wireshark's audio player, it doesn't get played. The sample rate was showing 0. And size of the .Au file is 151 MB and in .Raw format having size 5.39 MB. I'm running WS version 3.2.4. Request tell me how to convert this .Au file in a format so that windows media player can play it.

Eagle's avatar
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Eagle
asked 2020-08-28 01:29:07 +0000, updated 2020-08-28 01:32:48 +0000
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An RTP dynamic payload media type is identified during the session setup, e.g. with SDP as described in RFC 4566.

grahamb's avatar
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grahamb
answered 2020-08-28 11:54:40 +0000
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H.264 is a video codec, not playable with audio players.

Anders's avatar Anders (2020-08-28 12:32:52 +0000) edit
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Dear Sir ! You mean to say the .Au file I have saved post analysing in Wireshark, could still be played? As it was showing sample rate 0 while saving this payload in Wireshark. What does this sample rate=0 mean? Could you plz elaborate this More? Plz suggest me the better H.264 codec video player and plz send me the link to download SDP, as it is not available in free on open source. I hope you all eminent personnel would definitely help me. Regards 🙏

Eagle's avatar Eagle (2020-08-28 13:03:46 +0000) edit
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SDP is a protocol that is part of a conversation that sometimes precedes the RTP data, and indicates what type of format the data is in. Without the media description, you just have to guess at the encoding of the data.

grahamb's avatar grahamb (2020-08-28 13:20:36 +0000) edit
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Sir, am I required to download any software for this SDP ? And what all actions are to be taken after downloading this software if any? Is there any fixed syntax for SDP? or how is the SDP software going to work?

Eagle's avatar Eagle (2020-08-28 14:23:23 +0000) edit
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Nope, SDP can't be added after the fact, I suspect the information has been lost (or was never captured) in your capture.

You don't seem to understand RTP dynamic payloads.

A dynamic payload type can be ANY encoding type. Before the RTP traffic is sent, a session setup occurs (possibly by SIP\SDP) that says "In the following RTP data, the Dynamic Payload type XX will be encoded as YY" where XX is the dynamic payload type and YY is the identifier of the encoding.

It might be possible, with knowledge of encoding types, to determine by inspection of the data what the encoding is, I don't know if this can be done with your data. There may also be tools that can do this, but I don't know of any.

grahamb's avatar grahamb (2020-08-28 14:49:03 +0000) edit
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