943721 - MP4Reader should restrict its output codecs

Status: RESOLVED FIXED

(Core :: Audio/Video, defect)

Description

[Chris Pearce [:cpearce (Not reading bugmail)]]

MP4Reader doesn't limit the codecs that it passes to platform decoders to H.264 and AAC. It should. The mp4_demuxer denotes what codecs it's producing in the audio and video configs that it exposes, so this is easy.

Comment 1

[Chris Pearce [:cpearce (Not reading bugmail)]]

Attachment: Patch

Make MP4Reader restrict its codecs output to H.264 and AAC.

We should restrict the output of MP4Reader to H.264 and AAC so that we
don't end up invoking rogue platform decoders (if that's even possible).
This means that we won't play MP3 audio inside MP4, that's deliberate.

Comment 2

[Chris Pearce [:cpearce (Not reading bugmail)]]

I should point out that if and when we want to support other codecs, like MP3 audio, we'd need to change the PlatformDecoderModule::Create*Decoder() interface so that we could specify which codec we want to instantiate, and then add a decoder backend for each platform for that format.

So for MP3, the we'd need to add MediaDataDecoders for DirectShow, AppleMedia, OMX, and GStreamer (or whatever MP3 decoder we want to use). Possibly we could expose a fake MediaResource to the existing MediaDecoderReaders, like WebAudio does.

My point is that it's work to add support for MP3 decoding inside MP4, so I'm deliberately excluding it now.

Comment 3

[Chris Pearce [:cpearce (Not reading bugmail)]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/49a6738fa250

Comment 4

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/49a6738fa250