On 5/21/2020 10:24 PM, Andreas Rheinhardt wrote:
> av_stream_get_side_data() tells the caller whether a stream has side
> data of a specific type; if present it can also tell the caller the size
> of the side data via an optional argument. The Matroska muxer always
> used this optional argument, although it doesn't really need the size,
> as the relevant side-data are not buffers, but structures. So change
> this.
>
> Furthermore, relying on the size also made the code susceptible to
> a quirk of av_stream_get_side_data(): It only sets the size argument if
> it found side data of the desired type.
Sounds like something that should be fixed instead.
av_packet_get_side_data() sets the size argument to 0 if it doesn't find
the requested side data type. This function should do the same.
> mkv_write_video_color() checks
> for side-data twice with the same variable for the size without resetting
> the size in between; if the second type of side-data isn't present, the
> size will still be what it was after the first call. This was not
> dangerous in practice, as the check for the existence of the second
> side-data compared the size with the expected size, so it would only be
> problematic if lots of elements were to be added to AVContentLightMetadata.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@gmail.com>
> ---
> libavformat/matroskaenc.c | 19 ++++++++-----------
> 1 file changed, 8 insertions(+), 11 deletions(-)
>
> diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
> index fccfee539a..f5968c17b4 100644
> --- a/libavformat/matroskaenc.c
> +++ b/libavformat/matroskaenc.c
> @@ -835,7 +835,6 @@ static void mkv_write_video_color(AVIOContext *pb, const
> AVStream *st,
> * plus another byte to stay clear of the end. */
> uint8_t colour[(2 + 1 + 8) * 18 + (2 + 1) + 1];
> AVIOContext buf, *dyn_cp = &buf;
> - int side_data_size = 0;
> int colorinfo_size;
> const uint8_t *side_data;
>
> @@ -868,8 +867,8 @@ static void mkv_write_video_color(AVIOContext *pb, const
> AVStream *st,
> }
>
> side_data = av_stream_get_side_data(st, AV_PKT_DATA_CONTENT_LIGHT_LEVEL,
> - &side_data_size);
> - if (side_data_size) {
> + NULL);
> + if (side_data) {
> const AVContentLightMetadata *metadata =
> (const AVContentLightMetadata*)side_data;
> put_ebml_uint(dyn_cp, MATROSKA_ID_VIDEOCOLORMAXCLL,
> metadata->MaxCLL);
> @@ -877,8 +876,8 @@ static void mkv_write_video_color(AVIOContext *pb, const
> AVStream *st,
> }
>
> side_data = av_stream_get_side_data(st,
> AV_PKT_DATA_MASTERING_DISPLAY_METADATA,
> - &side_data_size);
> - if (side_data_size == sizeof(AVMasteringDisplayMetadata)) {
> + NULL);
> + if (side_data) {
> ebml_master meta_element = start_ebml_master(
> dyn_cp, MATROSKA_ID_VIDEOCOLORMASTERINGMETA, 10 * (2 + 1 + 8));
> const AVMasteringDisplayMetadata *metadata =
> @@ -919,14 +918,13 @@ static void mkv_write_video_projection(AVFormatContext
> *s, AVIOContext *pb,
> const AVStream *st)
> {
> ebml_master projection;
> - int side_data_size = 0;
> uint8_t private[20];
>
> const AVSphericalMapping *spherical =
> (const AVSphericalMapping *)av_stream_get_side_data(st,
> AV_PKT_DATA_SPHERICAL,
> - &side_data_size);
> + NULL);
>
> - if (!side_data_size)
> + if (!spherical)
> return;
>
> if (spherical->projection != AV_SPHERICAL_EQUIRECTANGULAR &&
> @@ -1028,7 +1026,6 @@ static int mkv_write_stereo_mode(AVFormatContext *s,
> AVIOContext *pb,
> const AVDictionaryEntry *tag;
> MatroskaVideoStereoModeType format = MATROSKA_VIDEO_STEREOMODE_TYPE_NB;
> const AVStereo3D *stereo;
> - int side_data_size = 0;
>
> *h_width = 1;
> *h_height = 1;
> @@ -1052,8 +1049,8 @@ static int mkv_write_stereo_mode(AVFormatContext *s,
> AVIOContext *pb,
> }
>
> stereo = (const AVStereo3D*)av_stream_get_side_data(st,
> AV_PKT_DATA_STEREO3D,
> - &side_data_size);
> - if (side_data_size >= sizeof(AVStereo3D)) {
> + NULL);
> + if (stereo) {
> switch (stereo->type) {
> case AV_STEREO3D_2D:
> format = MATROSKA_VIDEO_STEREOMODE_TYPE_MONO;
>
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