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vtenc: Signal ignored alpha component with ProRes

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When the image is opaque but the output ProRes format has an alpha
component (4 component, 32 bits per pixel), Apple requires that we
signal that it should be ignored by setting the depth to 24 bits per
pixel. Not doing so causes the encoded files to fail validation.

So we set that in the caps and qtmux sets the depth value in the
container, which will be read by demuxers so that decoders can skip
those bytes entirely. qtdemux does this, but vtdec does not use this
information at present.

The sister change was made in qtmux and qtdemux in:
https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/1061

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1489>
This commit is contained in:
Nirbheek Chauhan 2022-01-03 21:02:47 +05:30 committed by GStreamer Marge Bot
parent e1f9c6d559
commit 6b7d819c25
1 changed files with 24 additions and 0 deletions
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24
subprojects/gst-plugins-bad/sys/applemedia/vtenc.c
View file

@ -821,6 +821,28 @@ gst_vtenc_is_negotiated (GstVTEnc * self)
return self->negotiated_width != 0;
}
/*
* When the image is opaque but the output ProRes format has an alpha
* component (4 component, 32 bits per pixel), Apple requires that we signal
* that it should be ignored by setting the depth to 24 bits per pixel. Not
* doing so causes the encoded files to fail validation.
*
* So we set that in the caps and qtmux sets the depth value in the container,
* which will be read by demuxers so that decoders can skip those bytes
* entirely. qtdemux does this, but vtdec does not use this information at
* present.
*/
static gboolean
gst_vtenc_signal_ignored_alpha_component (GstVTEnc * self)
{
if (self->preserve_alpha)
return FALSE;
if (self->specific_format_id == kCMVideoCodecType_AppleProRes4444XQ ||
self->specific_format_id == kCMVideoCodecType_AppleProRes4444)
return TRUE;
return FALSE;
}
static gboolean
gst_vtenc_negotiate_downstream (GstVTEnc * self, CMSampleBufferRef sbuf)
{
@ -884,6 +906,8 @@ gst_vtenc_negotiate_downstream (GstVTEnc * self, CMSampleBufferRef sbuf)
gst_structure_set (s, "variant", G_TYPE_STRING,
gst_vtutil_codec_type_to_prores_variant (self->specific_format_id),
NULL);
if (gst_vtenc_signal_ignored_alpha_component (self))
gst_structure_set (s, "depth", G_TYPE_INT, 24, NULL);
break;
default:
g_assert_not_reached ();