RTSP support for iOS

[pAlkesz]

Hi all!

First of all great library, using it is infinitely more convenient compared to the old VLC libs.

My question is, in its current state does this library support RTSP streaming on iOS? From the README.md file I gather that the answer would be yes because RTSP is specifically mentioned in the supported formats of the showcase app. However so far I could not get RTSP to work neither in my own app nor the showcase app.

What I am doing is just giving a local rtsp url to the player without any special stuff and my expectation is that the stream plays. However all I get in the logs are these "Failed to play RTSP session" messages. When I enabled verbose logging this is the output I get back:

[libvlc libvlc] Creating an input for playback'rtsp://CAMERA_HOST:8554/live'
[libvlc libvlc] creating audio output
[libvlc libvlc] looking for audio output module matching "any": 2 candidates
[libvlc libvlc] using audio output module "avsamplebuffer"
[libvlc libvlc] keeping audio output
[libvlc libvlc] Creating an input for playback'rtsp://CAMERA_HOST:8554/live'
[libvlc libvlc] using timeshift granularity of 50 MiB
[libvlc libvlc] using default timeshift path
[libvlc libvlc] rtsp://CAMERA_HOST:8554/live' gives access rtsp' demux any' path CAMERA_HOST:8554/live'
[libvlc libvlc] creating access: rtsp://CAMERA_HOST:8554/live
[libvlc libvlc] looking for access module matching "rtsp": 1 candidates
[libvlc libvlc] try to open 'rtsp://CAMERA_HOST:8554/live'
[libvlc libvlc] connect to host 'CAMERA_HOST'
[libvlc libvlc] removing "audio output" module "avsamplebuffer"
[libvlc libvlc] connection succeeded (socket = 17)
[libvlc libvlc] net: opening 0.0.0.0 datagram port 9278
[libvlc libvlc] net: opening 0.0.0.0 datagram port 9279
[libvlc libvlc] Failed to play RTSP session
[libvlc libvlc] Failed to teardown RTSP session
[libvlc libvlc] no access modules matched with name rtsp

According to my all knowing AI agent the issue is that its trying to open the RTSP stream using satip which is not an RTSP client. The real RTSP client module would be live555 which is missing from this libVLC build. I have no clue about the inner workings of VLC so take this diagnosis with a grain of salt, might be total nonsense.

Anyhow I would greatly appreciate any information about RTSP support, I have not posted code yet since I am not sure if this issue is known or not but let me know if you do not experience the same thing on your end and then I will try to provide a repro project.

Cheers,
Paul

[omaralbeik]

Your diagnosis is right, and thanks for the verbose log, it made this quick to pin down.

There is no RTSP client in the current build. live555 is the module that handles rtsp:// in VLC, and it never gets compiled. VLC's Apple build config (extras/package/apple/build.conf) passes --disable-gpl --disable-gnuv3 to the contrib bootstrap, and live555 is gated behind GNUV3 in contrib/src/live555/rules.mak, so it is skipped. I dumped the module table out of the shipped libvlc.a to be sure: 289 modules registered, no live555 among them.

That leaves satip as the only module claiming the rtsp shortcut, because modules/access/satip.c declares add_shortcut("rtsp", "satip"). That is exactly your 1 candidates line. SAT>IP is a DVB tuner protocol that happens to use RTSP for signaling, so it connects to your camera and then fails on PLAY, which is the "Failed to play RTSP session" you are seeing.

So no repro project needed. This fails for any rtsp:// URL, on every platform we ship, not just iOS.

There is also no workaround on the current binary, in case you were about to go looking. avio only claims the rtmp shortcuts, and its avio:// form goes through avio_open2, which resolves protocols and not demuxers, so it cannot reach FFmpeg's RTSP demuxer. avformat is registered as a demux rather than an access_demux, so it wants a byte stream that rtsp:// never gives it.

Fixing this means rebuilding libVLC with live555 in it. The catch is licensing. live555 relicensed to LGPLv3 in late 2016, which is why the Apple build drops it by default, and LGPLv3 static linking is a problem for App Store apps. VLCKit deals with this by pinning live555 to 2016.10.21, the last LGPLv2.1 release, and removing the GNUV3 gate. I want to try the same thing here. The open question is whether a 2016 live555 still compiles against VLC 4, since VLCKit is on VLC 3.

Separately, the README should not be listing RTSP as supported while this is broken. Fixing that now.

Keeping this issue open to track the live555 work.