| Message ID | 20240131230136.30924-1-cus@passwd.hu |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
Quoting Marton Balint (2024-02-01 00:01:36) > diff --git a/libavutil/channel_layout.h b/libavutil/channel_layout.h > index 37629ab5d2..7e27a00d39 100644 > --- a/libavutil/channel_layout.h > +++ b/libavutil/channel_layout.h > @@ -817,6 +817,17 @@ int av_channel_layout_check(const AVChannelLayout *channel_layout); > */ > int av_channel_layout_compare(const AVChannelLayout *chl, const AVChannelLayout *chl1); > > +/** > + * Try changing the AVChannelOrder of a channel layout. What exactly is the rule for when the change succeeds or not? I would expect it to be when all the channels can be represented in the new order, but that is not the case for conversion to unspec. > + * > + * @param channel_layout channel layout which will be changed > + * @param order the desired channel layout order > + * @return 0 on success or if the channel layout is already in the desired order > + * 1 if using the desired order is not possible for the specified layout AVERROR(ENOSYS) seems more consistent to me
On Thu, 1 Feb 2024, Anton Khirnov wrote: > Quoting Marton Balint (2024-02-01 00:01:36) >> diff --git a/libavutil/channel_layout.h b/libavutil/channel_layout.h >> index 37629ab5d2..7e27a00d39 100644 >> --- a/libavutil/channel_layout.h >> +++ b/libavutil/channel_layout.h >> @@ -817,6 +817,17 @@ int av_channel_layout_check(const AVChannelLayout *channel_layout); >> */ >> int av_channel_layout_compare(const AVChannelLayout *chl, const AVChannelLayout *chl1); >> >> +/** >> + * Try changing the AVChannelOrder of a channel layout. > > What exactly is the rule for when the change succeeds or not? I would > expect it to be when all the channels can be represented in the new > order, but that is not the case for conversion to unspec. Yes, you are right. Converting to unspec indeed makes you lose the channel designations, so the conversion will not be lossless. On the other hand, when you specify UNSPEC as a target, you don't actually expect to keep the designations, so what is the point of returning an error... I think this is one of those cases when both behaviour (always doing the conversion, or returning a failure in case the source order is not already unspec) can make sense. We have to decide though if a custom layout with all channels as UNKNOWN can be losslessly converted to UNSPEC layout or not. And if yes, then would not that conflict with av_channel_layout_channel_from_index() which returns AV_CHAN_NONE and not AV_CHAN_UNKNOWN for UNSPEC layouts... So if you have a preference, I can change this (and document it), I don't particularly feel strongly about any of the two approaches. Probably there is no bad choce as long as it is properly documented. > >> + * >> + * @param channel_layout channel layout which will be changed >> + * @param order the desired channel layout order >> + * @return 0 on success or if the channel layout is already in the desired order >> + * 1 if using the desired order is not possible for the specified layout > > AVERROR(ENOSYS) seems more consistent to me By using a positive result all negative return values can be considered serious errors which have to be propagated back to the user. In the next patch I try to simplify a custom channel layout: + ret = av_channel_layout_retype(ch_layout, AV_CHANNEL_ORDER_NATIVE); + if (ret < 0) + goto out; I can do simply this, because I don't care if the simplification was successful. Regards, Marton
Quoting Marton Balint (2024-02-01 21:36:31) > > What exactly is the rule for when the change succeeds or not? I would > > expect it to be when all the channels can be represented in the new > > order, but that is not the case for conversion to unspec. > > Yes, you are right. Converting to unspec indeed makes you lose the > channel designations, so the conversion will not be lossless. On the other > hand, when you specify UNSPEC as a target, you don't actually expect to > keep the designations, so what is the point of returning an error... > > I think this is one of those cases when both behaviour (always doing the > conversion, or returning a failure in case the source order is not already > unspec) can make sense. We have to decide though if a custom layout with > all channels as UNKNOWN can be losslessly converted to UNSPEC layout or > not. And if yes, then would not that conflict with > av_channel_layout_channel_from_index() which returns AV_CHAN_NONE and not > AV_CHAN_UNKNOWN for UNSPEC layouts... Huh, that might actually considered a bug, returning UNKNOWN certainly makes more sense to me. > > > >> + * > >> + * @param channel_layout channel layout which will be changed > >> + * @param order the desired channel layout order > >> + * @return 0 on success or if the channel layout is already in the desired order > >> + * 1 if using the desired order is not possible for the specified layout > > > > AVERROR(ENOSYS) seems more consistent to me > > By using a positive result all negative return values can be considered > serious errors which have to be propagated back to the user. > > In the next patch I try to simplify a custom channel layout: > > + ret = av_channel_layout_retype(ch_layout, AV_CHANNEL_ORDER_NATIVE); > + if (ret < 0) > + goto out; > > I can do simply this, because I don't care if the simplification was > successful. IMO policy like what errors are to be considered serious should be up to the caller. If you asked it to get a certain order and it failed to deliver, then I'd consider that an error state.
diff --git a/doc/APIchanges b/doc/APIchanges index 8e8498f803..ce1e816fa5 100644 --- a/doc/APIchanges +++ b/doc/APIchanges @@ -2,6 +2,9 @@ The last version increases of all libraries were on 2023-02-09 API changes, most recent first: +2024-02-xx - xxxxxxxxxx - lavu 58.38.100 - channel_layout.h + Add av_channel_layout_retype(). + 2024-02-xx - xxxxxxxxxx - lavu 58.37.100 - channel_layout.h Add av_channel_layout_from_custom(). diff --git a/libavutil/channel_layout.c b/libavutil/channel_layout.c index 0810d32bf6..056b7f7c10 100644 --- a/libavutil/channel_layout.c +++ b/libavutil/channel_layout.c @@ -1036,3 +1036,77 @@ uint64_t av_channel_layout_subset(const AVChannelLayout *channel_layout, return ret; } + +static int64_t masked_description(AVChannelLayout *channel_layout, int start_channel) +{ + uint64_t mask = 0; + for (int i = start_channel; i < channel_layout->nb_channels; i++) { + enum AVChannel ch = channel_layout->u.map[i].id; + if (ch >= 0 && ch < 63 && mask < (1ULL << ch)) + mask |= (1ULL << ch); + else + return AVERROR(EINVAL); + } + return mask; +} + +int av_channel_layout_retype(AVChannelLayout *channel_layout, enum AVChannelOrder order) +{ + if (!av_channel_layout_check(channel_layout)) + return AVERROR(EINVAL); + + if (channel_layout->order == order) + return 0; + + switch (order) { + case AV_CHANNEL_ORDER_UNSPEC: { + int nb_channels = channel_layout->nb_channels; + av_channel_layout_uninit(channel_layout); + channel_layout->order = AV_CHANNEL_ORDER_UNSPEC; + channel_layout->nb_channels = nb_channels; + return 0; + } + case AV_CHANNEL_ORDER_CUSTOM: { + AVChannelLayout custom = { 0 }; + int ret = av_channel_layout_from_custom(&custom, channel_layout->nb_channels); + if (ret < 0) + return ret; + if (channel_layout->order != AV_CHANNEL_ORDER_UNSPEC) + for (int i = 0; i < channel_layout->nb_channels; i++) + custom.u.map[i].id = av_channel_layout_channel_from_index(channel_layout, i); + av_channel_layout_uninit(channel_layout); + *channel_layout = custom; + return 0; + } + case AV_CHANNEL_ORDER_NATIVE: + if (channel_layout->order == AV_CHANNEL_ORDER_CUSTOM) { + int64_t mask = masked_description(channel_layout, 0); + if (mask < 0) + return 1; + av_channel_layout_uninit(channel_layout); + return av_channel_layout_from_mask(channel_layout, mask); + } else { + return 1; + } + case AV_CHANNEL_ORDER_AMBISONIC: + if (channel_layout->order == AV_CHANNEL_ORDER_CUSTOM) { + int64_t mask; + int nb_channels = channel_layout->nb_channels; + int order = ambisonic_order(channel_layout); + if (order < 0) + return 1; + mask = masked_description(channel_layout, (order + 1) * (order + 1)); + if (mask < 0) + return 1; + av_channel_layout_uninit(channel_layout); + channel_layout->order = AV_CHANNEL_ORDER_AMBISONIC; + channel_layout->nb_channels = nb_channels; + channel_layout->u.mask = mask; + return 0; + } else { + return 1; + } + default: + return 1; + } +} diff --git a/libavutil/channel_layout.h b/libavutil/channel_layout.h index 37629ab5d2..7e27a00d39 100644 --- a/libavutil/channel_layout.h +++ b/libavutil/channel_layout.h @@ -817,6 +817,17 @@ int av_channel_layout_check(const AVChannelLayout *channel_layout); */ int av_channel_layout_compare(const AVChannelLayout *chl, const AVChannelLayout *chl1); +/** + * Try changing the AVChannelOrder of a channel layout. + * + * @param channel_layout channel layout which will be changed + * @param order the desired channel layout order + * @return 0 on success or if the channel layout is already in the desired order + * 1 if using the desired order is not possible for the specified layout + * AVERROR code on error + */ +int av_channel_layout_retype(AVChannelLayout *channel_layout, enum AVChannelOrder order); + /** * @} */ diff --git a/libavutil/version.h b/libavutil/version.h index 3b38f8f5da..cebf4a0acd 100644 --- a/libavutil/version.h +++ b/libavutil/version.h @@ -79,7 +79,7 @@ */ #define LIBAVUTIL_VERSION_MAJOR 58 -#define LIBAVUTIL_VERSION_MINOR 37 +#define LIBAVUTIL_VERSION_MINOR 38 #define LIBAVUTIL_VERSION_MICRO 100 #define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
v2: add conversion from custom layout to ambisonic Signed-off-by: Marton Balint <cus@passwd.hu> --- doc/APIchanges | 3 ++ libavutil/channel_layout.c | 74 ++++++++++++++++++++++++++++++++++++++ libavutil/channel_layout.h | 11 ++++++ libavutil/version.h | 2 +- 4 files changed, 89 insertions(+), 1 deletion(-)