Hopefully it can support AVS3-P3 (Audio Vivid) decoding

[6hzzz]

SRC
AV3A sample
`Format : MPEG-4
Format profile : Base Media
Codec ID : isom (isom/iso2/mp41)
File size : 21.3 MiB
Duration : 3 min 32 s
Overall bit rate mode : Constant
Overall bit rate : 840 kb/s
Title : 偏心
Album : Leslie Cheung Final Encounter of The Legend
Track name/Position : 2
Track name/Total : 28
Performer : 張國榮
Writing application : Lavf60.21.101
Cover : Yes
Cover type : Cover
Audio
ID : 1
Format : av3a
Codec ID : av3a
Duration : 3 min 32 s
Bit rate mode : Constant
Bit rate : 832 kb/s
Sampling rate : 48.0 kHz
Stream size : 21.1 MiB (99%)
Title : AudioVivid10CH
Default : Yes
Alternate group : 1

Image
Type : Cover
Format : JPEG
Muxing mode : moov-meta-covr
Width : 1 000 pixels
Height : 1 000 pixels
Color space : YUV
Chroma subsampling : 4:4:4
Bit depth : 8 bits
Compression mode : Lossy
Stream size : 200 KiB (1%)`

[guidocella]

This is a request for ffmpeg.