On 1/27/2017 2:27 PM, [email protected] wrote:
On Friday, January 27, 2017 at 3:27:15 PM UTC+1, [email protected] wrote:
I've been struggling with using WebRTC together with Janus.
I have an h264 camera that I can't alter the configuration for.
The profile-level-id seems to be 420029, which means:
profile is baseline (42 hex = 66 dec = baseline)
constraints 0
level-idc is 4.1
ICE never completes because I suspect FF just barfs on this for some reason,
and I couldn't, no matter how much debug I enabled, find where or why
specifically.
Chrome works perfectly, but not before offering back profile-id 42e01f (which
the main difference is level-idc is 3.1 instead of 4.1).
When I re-encoded the content using FFMPEG using an intermediate device,
setting exactly 42e01f then FF finished ICE and played the video (although this
is not a valid solution for my purposes)
Ideally I want to understand why FF (openh264) can't play 420029, since it
should be baseline, and if there is a fix.
One more important note: if I took a small clip of the stream to a .mp4 file
(no transcoding), and embed that in HTML5 video tag, FF plays it perfectly. So
the codec SHOULD work as is, but not it doesn't when it's coming over webrtc.
Very annoying!
Hi all, I managed to "fix" this by rewriting the profile-level-id from 42009 to
42e01f before handing the SDP to FF.
I agree it is a hack, but as FF clearly works with this, then why don't you
allow 42009?
The WG requirement is for Constrained Baseline, not Baseline, which is
what we offer/accept. It's the 'e0' portion that causes the problem;
see RFC 6184 for details on what's compatible for offer/answer. Yes,
the rules are annoying if you want to support talking to a client that
doesn't support the same profile you prefer. Officially, to support
ConstrainedBaseline and Baseline you need to offer both as separate
payload types (with independent FMTPs).
This is this same thing
(https://groups.google.com/forum/#!searchin/mozilla.dev.media/4200xx%7Csort:relevance/mozilla.dev.media/9_zkibr_Bus/8LioRaUODAAJ)
that was noted in the Janus list you referenced. And as you mention,
you can 'cheat' and claim it's constrained baseline even though it's
not, and in this case it will work. (Not every such edit will --- if
you tell it the profile is baseline when it's high, it will likely
fail.) And how well these edits work depend on details of
implementation of the decoders.
--
Randell Jesup, mozilla
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