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

[Lynne]

8 Dec 2021, 02:06 by jamrial at gmail.com:

> From: Anton Khirnov <anton at khirnov.net>
>
> The new API is more extensible and allows for custom layouts.
> More accurate information is exported, eg for decoders that do not
> set a channel layout, lavc will not make one up for them.
>
> Deprecate the old API working with just uint64_t bitmasks.
>
> Expanded and completed by Vittorio Giovara <vittorio.giovara at gmail.com>
> and James Almer <jamrial at gmail.com>.
> Signed-off-by: Vittorio Giovara <vittorio.giovara at gmail.com>
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>  libavutil/channel_layout.c | 498 ++++++++++++++++++++++++++++++------
>  libavutil/channel_layout.h | 510 ++++++++++++++++++++++++++++++++++---
>  libavutil/version.h        |   1 +
>  3 files changed, 906 insertions(+), 103 deletions(-)
>  
>  /**
>  * @}
> @@ -128,6 +199,157 @@ enum AVMatrixEncoding {
>  AV_MATRIX_ENCODING_NB
>  };
>  
> +/**
> + * @}
> + */
> +
> +/**
> + * An AVChannelCustom defines a single channel within a custom order layout
> + *
> + * Unlike most structures in FFmpeg, sizeof(AVChannelCustom) is a part of the
> + * public ABI.
> + *
> + * No new fields may be added to it without a major version bump.
> + */
> +typedef struct AVChannelCustom {
> +    enum AVChannel id;
> +} AVChannelCustom;
>

Consider adding a 25-byte or so of a description field string here that
would also be copied if the frame/layout is copied?
That way, users can assign a description label to each channel,
for example labeling each channel in a 255 channel custom layout
Opus stream used in production at a venue somewhere.
Also, consider additionally reserving 16-bytes here, just in case.

Rest looks fine.