9 Dec 2021, 14:12 by an...@khirnov.net:
> Quoting Lynne (2021-12-08 13:57:45)
>
>> 8 Dec 2021, 13:16 by an...@khirnov.net:
>>
>> > Quoting Lynne (2021-12-08 10:02:34)
>> >
>> >> 8 Dec 2021, 02:06 by jamr...@gmail.com:
>> >>
>> >> > From: Anton Khirnov <an...@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.giov...@gmail.com>
>> >> > and James Almer <jamr...@gmail.com>.
>> >> > Signed-off-by: Vittorio Giovara <vittorio.giov...@gmail.com>
>> >> > Signed-off-by: James Almer <jamr...@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.
>> >>
>> >
>> > That would enlarge the layout size by a significant amount. Keep in mind
>> > that this is all per frame. And for something that very few people would
>> > want to use.
>> >
>> > These descriptors, if anyone really needs them, can live in side data.
>> >
>>
>> That's fine with me.
>> Can we at least have an opaque uint64_t? I'd accept a uintptr_t,
>> or an int too, or even a single-byte uint8_t.
>>
>
> like this?
>
> diff --git a/libavutil/channel_layout.h b/libavutil/channel_layout.h
> index 7b77a74b61..7b2ba12532 100644
> --- a/libavutil/channel_layout.h
> +++ b/libavutil/channel_layout.h
> @@ -252,7 +252,8 @@ enum AVMatrixEncoding {
> * No new fields may be added to it without a major version bump.
> */
> typedef struct AVChannelCustom {
> - enum AVChannel id;
> + enum AVChannel id:16;
> + int reserved:16;
> } AVChannelCustom;
>
"reserved" rather than "opaque"?
16 bits for both? Could you keep the id as a plain (32-bit, on
a sane compiler) enum, since we may need to add flags, one
never knows, and make the opaque field a plain uint32_t?
64-bits per channel overall isn't too bad.
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