Insertion of Custom Codecs into Firefox WebRTC Implementation

[aam...@gmail.com]

Hi everyone,

I was interested in modifying the Firefox implementation of WebRTC (for my own purposes), specifically, adding the MPEG-4 FBA codec to the implementation. I noticed that in the /media directory or Firefox source, there is the WebRTC installation as well as several codec libraries.

I was wondering, how would I be able to add and use additional codec libraries to the Firefox implementation of WebRTC?

[Eric Rescorla]

You can use the Gecko Media Plugin facility recently landed in Firefox 33.

-Ekr


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[Randell Jesup]

On 7/21/2014 11:04 AM, Eric Rescorla wrote:
> On Sun, Jul 20, 2014 at 5:06 PM, <aam...@gmail.com> wrote:
>
>> Hi everyone,
>>
>> I was interested in modifying the Firefox implementation of WebRTC (for my
>> own purposes), specifically, adding the MPEG-4 FBA codec to the
>> implementation. I noticed that in the /media directory or Firefox source,
>> there is the WebRTC installation as well as several codec libraries.
>>
>> I was wondering, how would I be able to add and use additional codec
>> libraries to the Firefox implementation of WebRTC?
>
> You can use the Gecko Media Plugin facility recently landed in Firefox 33.

Note that to experiment with a different codec you could masquerade as
an H.264 GMP plugin (with your data hidden in what look like H.264
NALs). We use mode 1, which effectively lets you produce large binary
blobs of data that get fragmented by the RTP layer and reassembled for
you. Note that the code will make assumptions that the KeyFrame/etc
flags are set correctly.

To implement a full new codec requires a GMP plugin, and mods to the
media/webrtc/trunk/webrtc code (webrtc.org code in our tree) to
implement packetization/depacketization specific to that codec, and
smaller mods to media/webrtc/signaling/src/media to handle SDP
negotiation. Perhaps a few to signaling/src/media-conduit to handle
config parameters from SDP.

--
Randell Jesup, Mozilla

[Aamoy Gupta]

So just to paraphrase, if I had the source of this codec, I would have to build it, and then trick GMP into thinking that it is an NAL. Do you know in the WebRTC trunk which files I would have to modify for packetization besides "media/webrtc/signaling/src/media" or does that depend on the codec?

Sorry for all the clarification questions-- I am very new to this.

[Eric Rescorla]

On Mon, Jul 21, 2014 at 4:50 PM, Aamoy Gupta <aam...@gmail.com> wrote:

> So just to paraphrase, if I had the source of this codec, I would have to
> build it, and then trick GMP into thinking that it is an NAL.

For now, yes. This isn't that hard, as shown by:
http://dxr.mozilla.org/mozilla-central/source/dom/media/gmp-plugin/gmp-fake.cpp

> Do you know in the WebRTC trunk which files I would have to modify for
> packetization besides "media/webrtc/signaling/src/media" or does that
> depend on the codec?
>
> Sorry for all the clarification questions-- I am very new to this.
>
> On Monday, July 21, 2014 8:59:34 AM UTC-7, Randell Jesup wrote: