[FFmpeg-devel] [PATCH] allow high audio sample rates in mov/mp4 muxer

Justin Ruggles justin.ruggles
Sat Jun 12 17:26:24 CEST 2010

Baptiste Coudurier wrote:

> On 06/10/2010 01:27 PM, Justin Ruggles wrote:
>> Alex Converse wrote:
>>> On Thu, Jun 10, 2010 at 1:54 PM, Justin Ruggles
>>> <justin.ruggles at gmail.com>  wrote:
>>>> Hi,
>>>> This patch allows the use of sample rates>  65535 in mov/mp4 (e.g. 96kHz
>>>> and 192kHz).  I don't know where to find this info in the MP4 spec, but
>>>> this is how the MPEG-4 ALS Reference Software does it.
>>> It might also be a good idea to look at the AAC 88.2/96 kHz test vectors.
>> Well, it seems that it shouldn't be 0, but should be the actual sample
>> rate using more than 16 bits.  I guess the reserved value that follows
>> is no longer reserved.  I'll send a new patch soon.
> Humm, I don't feel confident about this.
> Can we ask ISO about this ?

Ok, so after some more research, it looks like the reference samples and
the specs are in agreement that the sample rate field is 16.16 fixed
point and that only the low 16 bits of the sample rate are written.  The
real sample rate is in the AudioSpecificConfig.

New patch attached which allows high sample rates, but only writes the
low 16-bits in the stsd.


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