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

Justin Ruggles justin.ruggles
Sun Jun 13 18:52:29 CEST 2010

Baptiste Coudurier wrote:

> On 6/12/10 8:26 AM, Justin Ruggles wrote:
>> 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.
> Can you please quote the specs ? Just for reference.

ISO 14496-12 3rd Ed. 2008  Sample Description Box, Semantics
SampleRate is the sampling rate expressed as a 16.16 fixed-point number


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