[jitsi-dev] RTP VP8 Recording


#1

Hi,
I have a “pcap" file about a video call.
The codec is VP8, and it contains just the video (without audio).
I need to convert the VP8 RTP in a “webm” file (or another file video).
To implement it, I have used JPCAP, to read all RTP packet, and your class “WebmDataSink.java” and “WebmWriter.java”, to save the RTP in “webm” file.
I have tried to play it with “VLC”, but the video is very bad.
Please, is it the right way to convert the RTP (with VP8 codec) in a video file?
Can You suggest me an easy way to record the RTP?

Thanks in advance
Francesco


#2

Are you just dumping the raw RTP packets out, or are you depacketizing them?

https://tools.ietf.org/html/draft-ietf-payload-vp8-17

If you look in RecorderRtpImpl.java you can see how this is done in the
recorder.

Basically they create a Processor, and set the output from it to the
WebmWriter.

There are a number of things that could be hurting your capture.

The stream is probably encrypted, it probably has FEC packets, it probably
has RED packets.

All of these packets have to basically be processed correctly to create the
original vp8 payload.

You probably should publish your source, it would be a lot easier to
identify the issues.

···

On Jun 26, 2016 5:36 AM, "Francesco Falanga" <francesco.falanga@gmail.com> wrote:

Hi,
I have a “pcap" file about a video call.
The codec is VP8, and it contains just the video (without audio).
I need to convert the VP8 RTP in a “webm” file (or another file video).
To implement it, I have used JPCAP, to read all RTP packet, and your class
“*WebmDataSink.java*” and “*WebmWriter.java*”, to save the RTP in “webm”
file.
I have tried to play it with “VLC”, but the video is very bad.
Please, is it the right way to convert the RTP (with VP8 codec) in a video
file?
Can You suggest me an easy way to record the RTP?

Thanks in advance
Francesco

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#3

Hi Thomas,
thanks for the answer.
Below in-line my comments in red.

Thanks again
Francesco

Are you just dumping the raw RTP packets out, or are you depacketizing them?

  FF: I have used JPCAP and Wireshark to capture all RTP packets, and the cap generated is the same.
    Below the link with the complete pcap (not just the RTP):
      "https://www.dropbox.com/s/l7vd53uy2vwbz0z/uno.pcap?dl=0 <https://www.dropbox.com/s/l7vd53uy2vwbz0z/uno.pcap?dl=0>"
    The first strange thing is the payload = 120.

https://tools.ietf.org/html/draft-ietf-payload-vp8-17
If you look in RecorderRtpImpl.java you can see how this is done in the recorder.

Basically they create a Processor, and set the output from it to the WebmWriter.

There are a number of things that could be hurting your capture.

The stream is probably encrypted, it probably has FEC packets, it probably has RED packets.

All of these packets have to basically be processed correctly to create the original vp8 payload.

You probably should publish your source, it would be a lot easier to identify the issues.

  FF: in attachment my class to save the web file. Anyway, I have just extracted your “WebDataSink” with some changes.
    The method “transferData”, receive the RTP packet, and in it I implement the followings steps:
      - set the offset to “16” (12 byte RTP header + 4 VP8 header description)
      - remove the 12 byte RTP header, before to save the frame.

WebmDataSink.txt (13.1 KB)

···

On 26 Jun 2016, at 17:43, Jason Thomas <mail@jasonthom.as> wrote:

On Jun 26, 2016 5:36 AM, "Francesco Falanga" <francesco.falanga@gmail.com <mailto:francesco.falanga@gmail.com>> wrote:
Hi,
I have a “pcap" file about a video call.
The codec is VP8, and it contains just the video (without audio).
I need to convert the VP8 RTP in a “webm” file (or another file video).
To implement it, I have used JPCAP, to read all RTP packet, and your class “WebmDataSink.java” and “WebmWriter.java”, to save the RTP in “webm” file.
I have tried to play it with “VLC”, but the video is very bad.
Please, is it the right way to convert the RTP (with VP8 codec) in a video file?
Can You suggest me an easy way to record the RTP?

Thanks in advance
Francesco

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