Webrtcbin, chrome, and h264

[Trey Hutcheson]

Wow that was it. h264parse's config interval! Thank you so much.
Fortunately I still had that branch and that one property change got me
going.

You are a lifesaver. And I'm a total h264 newb. Again, thanks.

On Wed, Dec 9, 2020 at 3:46 PM Sean DuBois <sean at siobud.com> wrote:

> Hey,
>
> Lots of things can go wrong here, but these are the big ones I have run
> into!
>
> * Make sure you have a SPS/PPS with every IDR. GStreamer doesn't do that
>   by default. `config-interval=-1` on `h264parse` will fix that.
>
> * Make sure your PayloadTypes/SSRCes are correct. I don't believe this
>   is the issue since Chrome sees the incoming media. But I see this bite
>   a lot of people when the implementation doesn't handle this for them.
>
> * Make sure your browser supports the H264 profile. I don't believe this
>   is an issue since you are doing Chrome <-> Chrome. One thing to note
>   that Chrome doesn't support H264 on all platforms (Chromium on Debian
>   has no H264, and Android builds with hardware support)
>
> * General packet loss/ordering woes? Repacketizing could be exacerbating
>   issues. You could be transforming an out of order/lossy stream to an
>   in order one.
>
> * Lots of other possible issues :) I would try saving the RTP stream to
>   disk and using a tool to analyze it further. Just so you can know all
>   the attributes you are working with.
>
> On Wed, Dec 09, 2020 at 01:52:29PM -0600, Trey Hutcheson wrote:
> > I can't get Chrome to understand or render h264 content sent by another
> > chrome peer. Honestly I have no idea where the problem is. Here's the
> > scenario:
> > * chrome (87) produces an offer with h264 video, sendonly, and connects
> to
> > one instance of webrtcbin
> > * A second remote peer connects to a second instance of webrtcbin. In
> this
> > case, webrtcbin produces the offer. I connect video content received from
> > webrtcbin1 to webrtcbin2, by repayloading (webrtcbin1 > rtph264depay >
> > rtph264pay > webrtcbin2). Webrtcbin produces an offer with h264 video.
> The
> > second chrome peer  responds with an answer, accepting the offer.
> > * The second chrome peer fires the ontrack event for the new video
> stream,
> > but it doesn't actually understand the video. I've attached the stream
> to a
> > video element, but it doesn't render. Furthermore,
> > chrome://webrtc-internals reports "unknown" for the codec and the
> > decoderImplementation.
> >
> > Now, to narrow things down, on the server side I have tried taking the
> > stream received from webrtcbin1 and rendering it onscreen (rtp624depay
> > ! avdec_h264 ! videoconvert ! videoscale ! autovideosink) and it renders
> > just fine, proving that at the least the rtp is decoded properly and the
> > h264 decode process produces good video. Thus - the chrome provided video
> > must be correct.
> >
> > I've also tried inserting an h264parse element between the depay and
> > payload elements, and that had no effect.
> >
> > I have *also* tried depayloading, decoding, re-encoding, and
> re-payloading,
> > and that works just fine. Remote side understands the stream.
> >
> > For the record, I'm using the following code to make chrome provide h264:
> >
> > const video_transceiver = peer.addTransceiver('video', {"direction":
> > "sendonly"})
> > const capabilities = RTCRtpSender.getCapabilities('video')
> > const noVP8 = capabilities.codecs
> >     .filter(codec => codec.mimeType.toLocaleLowerCase() != "video/vp8")
> >     .filter(codec => codec.mimeType.toLocaleLowerCase() != "video/vp9");
> > video_transceiver.setCodecPreferences(noVP8);
> >
> > Does anyone have any insight?
>
> > _______________________________________________
> > gstreamer-devel mailing list
> > gstreamer-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>
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