[FFmpeg-devel] [PATCH 001/279] Add a new channel layout API

[Marton Balint]

On Wed, 8 Dec 2021, Lynne wrote:

> 8 Dec 2021, 10:22 by h.leppkes at gmail.com:
>
>> On Wed, Dec 8, 2021 at 10:14 AM Lynne <dev at lynne.ee> wrote:
>>
>>>
>>> 8 Dec 2021, 02:06 by jamrial at gmail.com:
>>>
>>>>
>>>> +enum AVChannel {
>>>> +    ///< Invalid channel index
>>>> +    AV_CHAN_NONE = -1,
>>>> +    AV_CHAN_FRONT_LEFT,
>>>>
>>>
>>> No, not the pixfmt mistake again. Set AV_CHAN_NONE to 0,
>>> the rest can follow. Or keep AV_CHAN_NONE to -1
>>> and add a new AV_CHAN_UNSPECIFIED as 0.
>>>
>>
>> Care to elaborate on the reasons of this opinion? Using -1 as invalid
>> and 0...x as valid entries seems quite reasonable to me.
>>
>
> Zero-initialization. I've had issues in the past telling
> YUV420P from <uninitialized>.

It is convenient to be able to set the channel 
layout mask by a simple byte shift of the ID-s.

AV_CH_FRONT_LEFT = 1 << AV_CHAN_FRONT_LEFT.

So I'd say that is the reason that it is designed that way, because this 
way existing channel layout masks can be kept without breaking ABI.

Regards,
Marton