Membrane RTSP source

ConnorRigby

Nerves Core Team

I’m building a project for streaming audio/video from a network webcam. I’ve successfully managed to get h264 stream data after modifying the built in Transport. I believe my next goal is to set it up to be a a Membrane Source, but i can’t find any existing documentation in the hexdocs for this.

Has anyone built their own membrane Source?
Am i on the right track or way off?

44 comments

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2020-09-27 17:56:03 UTC

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arruah

I have a task to transcode rtsp streams from ip video cameras and get a webrtc stream. As it is done here. This solution in golang does not use third-party services (ffmpeg or gstreamer). Can I do it with Membrane and Elixir? If so, can you tell me if there are any similar examples somewhere?

Post #44

entone

UDP FTW … Discord won’t let me post just acronyms, haha

Post #43

ConnorRigby

Nerves Core Team

So after some time working with it, i learned that RTSP supports using UDP for the media stream which gets rid of the RTSP interlacing as every packet ends up being a RTP packet. I haven’t decided which method i will use overall, but i suspect the UDP transport will be easier in the long run for me.

Post #42

mat-hek

Membrane Core Team

Perfect! Really glad you made it work And thanks for all the PRs

Post #41

ConnorRigby

Nerves Core Team

@mat-hek Good news! i found a bug in the code that was sending the SPS and PPS values to the parser. Was essentially causing an off by X number of bytes issue. Currently working on a PR to the ffmpeg element.

Post #40

ConnorRigby

Nerves Core Team

It prints it pretty constantly. I haven’t checked exactly but it looks like it happens on every frame. These logs weren’t here before i sent the sps and pps values to the parser. I’ll double check that it’s being sent/forwarded correctly.

Post #39

mat-hek

Membrane Core Team

ConnorRigby:

[h264 @ 0x7f78d002a7c0] Frame num change from 0 to 1
[h264 @ 0x7f78d002a7c0] decode_slice_header error
[h264 @ 0x7f78d002a7c0] error while decoding MB 15 1, bytestream -20
[h264 @ 0x7f78d002a7c0] concealing 8074 DC, 8074 AC, 8074 MV errors in P frame
[h264 @ 0x7f78d002a7c0] error while decoding MB 39 1, bytestream -6
[h264 @ 0x7f78d002a7c0] concealing 8050 DC, 8050 AC, 8050 MV errors in P frame
[h264 @ 0x7f78d002a7c0] error while decoding MB 19 1, bytestream -12
[h264 @ 0x7f78d002a7c0] concealing 8070 DC, 8070 AC, 8070 MV errors in P frame

These logs mean that the decoder is able to parse all the headers and metadata, but some parts of the stream content (actual video) are malformed/incompatible. How often is that printed? I suppose it might have occurred before, but you didn’t see it because of the amount of non-existing PPS 0 referenced logs. Also, make sure that parameter sets are not duplicated - both provided to the decoder via options and forwarded there by the parser (the second way is the best solution imho).

Silencing logs may not be the best way to go, as they can possibly carry some useful information in case of failure.

Post #38

xlphs

FFmpeg has an option to silence logs by changing log level, maybe try that.

Post #37

ConnorRigby

Nerves Core Team

yes i’m getting valid video, but every RTP frame that is parsed/decoded logs that non-existing PPS 0 referenced error. Like nothing bad seems to be happeneing, just an annoying log.

Post #36

xlphs

You are getting video as expected but the PPS error comes with every frame? It sounds like the decoder is now overzealous in making sure sps/pps are present