On 1/27/2017 5:12 PM, Aaron Colwell wrote:
> Adding support for writing spherical metadata in Matroska.
>
>
> 0001-matroskaenc-Add-support-for-writing-video-projection.patch
>
>
> From 5a9cf56bf3114186412bb5572b153f886edb6ddb Mon Sep 17 00:00:00 2001
> From: Aaron Colwell <acolw...@google.com>
> Date: Fri, 27 Jan 2017 12:07:25 -0800
> Subject: [PATCH] matroskaenc: Add support for writing video projection
> element.
>
> Adding support for writing spherical metadata in Matroska.
> ---
> libavformat/matroskaenc.c | 64
> +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 64 insertions(+)
>
> diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
> index f731b678b9..1b186db223 100644
> --- a/libavformat/matroskaenc.c
> +++ b/libavformat/matroskaenc.c
> @@ -1038,6 +1038,67 @@ static int mkv_write_stereo_mode(AVFormatContext *s,
> AVIOContext *pb,
> return ret;
> }
>
> +static int mkv_write_video_projection(AVIOContext *pb, AVStream *st)
> +{
> + AVSphericalMapping *spherical_mapping =
> (AVSphericalMapping*)av_stream_get_side_data(st, AV_PKT_DATA_SPHERICAL, NULL);
> + ebml_master projection;
> + int projection_type = 0;
> +
> + AVIOContext *dyn_cp;
> + uint8_t *projection_private_ptr = NULL;
> + int ret, projection_private_size;
> +
> + if (!spherical_mapping)
> + return 0;
> +
> + if (spherical_mapping->projection != AV_SPHERICAL_EQUIRECTANGULAR &&
> + spherical_mapping->projection != AV_SPHERICAL_CUBEMAP) {
> + av_log(pb, AV_LOG_WARNING, "Unsupported projection %d. projection
> not written.\n", spherical_mapping->projection);
> + return 0;
> + }
> +
> + ret = avio_open_dyn_buf(&dyn_cp);
> + if (ret < 0)
> + return ret;
> +
> + switch (spherical_mapping->projection) {
> + case AV_SPHERICAL_EQUIRECTANGULAR:
> + projection_type = 1;
> +
> + /* Create ProjectionPrivate contents */
> + avio_wb32(dyn_cp, 0); /* version = 0 & flags = 0 */
> + avio_wb32(dyn_cp, 0); /* projection_bounds_top */
> + avio_wb32(dyn_cp, 0); /* projection_bounds_bottom */
> + avio_wb32(dyn_cp, 0); /* projection_bounds_left */
> + avio_wb32(dyn_cp, 0); /* projection_bounds_right */
You could instead use a local 20 byte array, fill it using AV_WB32() and
then write it with put_ebml_binary().
Also, the latest change to the spec draft mentions ProjectionPrivate is
optional for Equirectangular projections if the contents are going to be
all zero.
> + break;
> + case AV_SPHERICAL_CUBEMAP:
> + projection_type = 2;
> +
> + /* Create ProjectionPrivate contents */
> + avio_wb32(dyn_cp, 0); /* version = 0 & flags = 0 */
> + avio_wb32(dyn_cp, 0); /* layout */
> + avio_wb32(dyn_cp, 0); /* padding */
> + break;
> + }
Same, 12 byte array.
What if the user is trying to remux a matroska file that has a
ProjectionPrivate element or an mp4 with an equi box filled with non zero
values, for that matter?
I know you're the one behind the spec in question, but wouldn't it be a
better idea to wait until AVSphericalMapping gets a way to propagate this
kind of information before adding support for muxing video projection
elements? Or maybe try to implement it right now...
This also applies to the mp4 patch.
> +
> + projection_private_size = avio_close_dyn_buf(dyn_cp,
> &projection_private_ptr);
The dynbuf should ideally contain the whole Projection master, so you can
then pass its size to start_ebml_master() instead of zero.
See mkv_write_video_color().
> +
> + projection = start_ebml_master(pb, MATROSKA_ID_VIDEOPROJECTION, 0);
> + put_ebml_uint(pb, MATROSKA_ID_VIDEOPROJECTIONTYPE, projection_type);
> + if (projection_private_size)
> + put_ebml_binary(pb, MATROSKA_ID_VIDEOPROJECTIONPRIVATE,
> projection_private_ptr, projection_private_size);
> +
> + put_ebml_float(pb, MATROSKA_ID_VIDEOPROJECTIONPOSEYAW,
> (float)(spherical_mapping->yaw) / (1 << 16));
> + put_ebml_float(pb, MATROSKA_ID_VIDEOPROJECTIONPOSEPITCH,
> (float)(spherical_mapping->pitch) / (1 << 16));
> + put_ebml_float(pb, MATROSKA_ID_VIDEOPROJECTIONPOSEROLL,
> (float)(spherical_mapping->roll) / (1 << 16));
> + end_ebml_master(pb, projection);
> +
> + av_free(projection_private_ptr);
> +
> + return 0;
> +}
> +
> static int mkv_write_track(AVFormatContext *s, MatroskaMuxContext *mkv,
> int i, AVIOContext *pb, int default_stream_exists)
> {
> @@ -1251,6 +1312,9 @@ static int mkv_write_track(AVFormatContext *s,
> MatroskaMuxContext *mkv,
> ret = mkv_write_video_color(pb, par, st);
> if (ret < 0)
> return ret;
> + ret = mkv_write_video_projection(pb, st);
This needs to be inside a check for strict experimental compliance
nonetheless.
> + if (ret < 0)
> + return ret;
> end_ebml_master(pb, subinfo);
> break;
>
> -- 2.11.0.483.g087da7b7c-goog
>
>
>
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