On Sat, 6 May 2017 15:30:35 +0200
Luca Barbato <lu_z...@gentoo.org> wrote:
> On 5/6/17 5:13 AM, wm4 wrote:
> > On Fri, 5 May 2017 22:20:18 -0400
> > Vittorio Giovara <vittorio.giov...@gmail.com> wrote:
> >
> >
> >> +enum AVChannelOrder {
> >> + /**
> >> + * The native channel order, i.e. the channels are in the same order
> >> in
> >> + * which they are defined in the AVChannel enum. This supports up to
> >> 63
> >> + * different channels.
> >> + */
> >> + AV_CHANNEL_ORDER_NATIVE,
> >> + /**
> >> + * The channel order does not correspond to any other predefined
> >> order and
> >> + * is stored as an explicit map. For example, this could be used to
> >> support
> >> + * layouts with 64 or more channels.
> >> + */
> >> + AV_CHANNEL_ORDER_CUSTOM,
> >> + /**
> >> + * Only the channel count is specified, without any further
> >> information
> >> + * about the channels.
> >> + */
> >> + AV_CHANNEL_ORDER_UNSPEC,
> >> +};
> >
> >
> >> +typedef struct AVChannelLayout {
> >> + /**
> >> + * Channel order used in this layout.
> >> + */
> >> + enum AVChannelOrder order;
> >> +
> >> + /**
> >> + * Number of channels in this layout. Mandatory field.
> >> + */
> >> + int nb_channels;
> >> +
> >> + /**
> >> + * Details about which channels are present in this layout.
> >> + * For AV_CHANNEL_ORDER_UNSPEC, this field is undefined and must not
> >> be
> >> + * used.
> >> + */
> >> + union {
> >> + /**
> >> + * This member must be used for AV_CHANNEL_ORDER_NATIVE.
> >> + * It is a bitmask, where the position of each set bit means that
> >> the
> >> + * AVChannel with the corresponding value is present.
> >> + *
> >> + * I.e. when (mask & (1 << AV_CHAN_FOO)) is non-zero, then
> >> AV_CHAN_FOO
> >> + * is present in the layout. Otherwise it is not present.
> >> + *
> >> + * @note when a channel layout using a bitmask is constructed or
> >> + * modified manually (i.e. not using any of the
> >> av_channel_layout_*
> >> + * functions), the code doing it must ensure that the number of
> >> set bits
> >> + * is equal to nb_channels.
> >> + */
> >> + uint64_t mask;
> >> + /**
> >> + * This member must be used when the channel order is not native,
> >> and
> >> + * represents a nb_channels-sized array. Its semantics may
> >> depending on
> >> + * the channel order.
> >> + *
> >> + * - For AV_CHANNEL_ORDER_CUSTOM: each element signals the
> >> presence of
> >> + * the AVChannel with the corresponding value: eg. when map[i]
> >> is
> >> + * equal to AV_CHAN_FOO, then AV_CHAN_FOO is the i-th channel in
> >> + * the audio data.
> >
> > Does it allow a channel to be mapped more than once? Does it allow
> > padding channels (that would be all-0)?
> >
> >> + */
> >> + uint8_t *map;
> >> + } u;
> >> +} AVChannelLayout;
> >
> > So AV_CHANNEL_ORDER_CUSTOM is as powerful as AV_CHANNEL_ORDER_NATIVE,
> > just that it allows an arbitrary order?
> >
> > How would layouts that don't fit into the channel label schema be
> > handled?
> >
> > How would that ambisonic stuff be represented?
>
> As a different AV_CHANNEL_ORDER
I'd still like to see it.
AFAIK the whole point of the patchset is because of ambisonics?
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