[FFmpeg-devel] [PATCH v5 1/2] lavf/isom: support for demuxing MPEG-H 3D Audio in MP4

Tsuchiya, Yuki (SHES) Yuki.Tsuchiya at sony.com
Fri Nov 22 10:40:40 EET 2019

> This is changing the muxer, but the commit subject and description talks about
> demuxing.
Yes. This code contains both the remuxer into MP4 and the demuxer. I will change the commit description
> You're calling this function for MPEGH 3D Audio, but not writing an
> implementation for it. The sgpd_entries array will be empty.
Thank you for pointing it out. 
In AAC case, the sgpd delay is set to -1 statically because most of popular AAC encoders have same encoder delay(1024 samples), but basically this value would be different for each encoder.
At this moment, there is no standard in MPEG-H 3D Audio so the value should not set statically.
In this patch, I'll remove this code. Most of media player could remove the encoder delay by using the edit list even if there is no sgpd box.

> Is every sample meant to be a Sync Sample?
No. The stss box is generated based on the sync frame flag information in MOVtrack. The sample MPEG-H 3D Audio content has sync frame in every 25 frame.

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