On 1/29/2024 8:27 PM, Marton Balint wrote:
Signed-off-by: Marton Balint <c...@passwd.hu>
---
doc/APIchanges | 3 +++
libavutil/channel_layout.c | 48 ++++++++++++++++++++++++++++++++++++++
libavutil/channel_layout.h | 11 +++++++++
libavutil/version.h | 2 +-
4 files changed, 63 insertions(+), 1 deletion(-)
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..cc8c208080 100644
--- a/libavutil/channel_layout.c
+++ b/libavutil/channel_layout.c
@@ -1036,3 +1036,51 @@ uint64_t av_channel_layout_subset(const AVChannelLayout
*channel_layout,
return ret;
}
+
+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) {
+ uint64_t mask = 0;
+ for (int i = 0; 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 1;
+ }
+ av_channel_layout_uninit(channel_layout);
+ return av_channel_layout_from_mask(channel_layout, mask);
+ } else {
+ return 1;
+ }
+ default:
+ return 1;
+ }
+}
I wrote a function like this some time ago, but i lost the patch by
accident during a migration.
The way i approached it was making the return codes reflect if the
conversion was lossless or not, as in, custom -> native is lossless only
if channels have no custom names (and possible only if the ids are
within UINT64_MAX and in order). Anything to Unspec is always lossy, etc.
Custom -> Ambi: Possible only if it contains ambi channels. Lossless.
Custom -> Native: Possible only if has no ambi channels and all ids < 64
and in order. Lossy if it has custom names, otherwise lossless.
Ambi -> Custom: Lossless.
Ambi -> Native: Not possible.
Native -> Custom: Lossless.
Native -> Ambi: Not possible.
Any -> Unspec: Possible but lossy.
So 0 for lossless, 1 for lossy, ENOSYS for not possible.
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