[FFmpeg-devel] avcodec/aacenc: Compatibility with Bluetooth A2DP headsets

[Andrey Semashev]

On 2019-12-24 01:57, Andrey Semashev wrote:
> Hi,
> 
> I'm trying to add support for AAC to PulseAudio with regard to Bluetooth 
> A2DP. I'm using libavcodec to encode AAC content and then packetize it 
> into RTP MP4-LATM packets, as required by A2DP spec. My current 
> implementation allows to switch between libfdk-aac and built-in AAC 
> encoder backends.
> 
> With libfdk-aac, everything's working well, the encoded audio is 
> correctly played by the BT headset (EOZ Air). But with the built-in 
> encoder I can hear occasional audio drop outs and artefacts like clicks 
> and weird stereo effects. I'm assuming this is because some decoding 
> errors on the headset, but obviously I don't have any kind of debug info 
> from it. When the same content is played (e.g. the same song) on 
> different runs, the artefacts appear at roughly the same places, so I'm 
> assuming that the problem is input content-related.
> 
> Given that libfdk-aac output is played without artefacts by the device, 
> I'm assuming my packetization code is correct. I also tried to debug and 
> analyze its output and didn't find anything out of order. This makes me 
> believe the problem is in the built-in encoder.
> 
> How should I proceed about this problem? What kind of information would 
> be useful to the aacenc developer(s) to debug this? Is there any 
> information as to how conforming aacenc is to the AAC spec and other, 
> especially hardware implementations?
> 
> For a start, here is my code:
> 
> https://gitlab.freedesktop.org/andrey.semashev/pulseaudio/blob/a2dp-codecs-aac/src/modules/bluetooth/a2dp-codec-aac.c 
> 
> 
> libavcodec encoder context initialization is at:
> 
> https://gitlab.freedesktop.org/andrey.semashev/pulseaudio/blob/a2dp-codecs-aac/src/modules/bluetooth/a2dp-codec-aac.c#L685 
> 
> 
> Thanks.

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