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Use tkhd matrix for proper display in mov.

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Patch by John Schmiederer jschmiederer on2 com
Original thread: [PATCH] Use tkhd matrix for proper display in mov
Date: 05/23/2008 09:31 PM

Originally committed as revision 14365 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
John Schmiederer 2008-07-24 07:55:11 +00:00 committed by Benoit Fouet
parent 2477d60944
commit ec072669f7
1 changed files with 33 additions and 4 deletions
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37
libavformat/mov.c
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@ -1371,6 +1371,11 @@ static int mov_read_udta(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
static int mov_read_tkhd(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
{
int i;
int width;
int height;
int64_t disp_transform[2];
int display_matrix[3][2];
AVStream *st = c->fc->streams[c->fc->nb_streams-1];
int version = get_byte(pb);
@ -1402,12 +1407,36 @@ static int mov_read_tkhd(MOVContext *c, ByteIOContext *pb, MOV_atom_t atom)
get_be16(pb); /* volume */
get_be16(pb); /* reserved */
url_fskip(pb, 36); /* display matrix */
//read in the display matrix (outlined in ISO 14496-12, Section 6.2.2)
// they're kept in fixed point format through all calculations
// ignore u,v,z b/c we don't need the scale factor to calc aspect ratio
for (i = 0; i < 3; i++) {
display_matrix[i][0] = get_be32(pb); // 16.16 fixed point
display_matrix[i][1] = get_be32(pb); // 16.16 fixed point
get_be32(pb); // 2.30 fixed point (not used)
}
/* those are fixed-point */
get_be32(pb); /* track width */
get_be32(pb); /* track height */
width = get_be32(pb); // 16.16 fixed point track width
height = get_be32(pb); // 16.16 fixed point track height
//transform the display width/height according to the matrix
// skip this if the display matrix is the default identity matrix
// to keep the same scale, use [width height 1<<16]
if (width && height &&
(display_matrix[0][0] != 65536 || display_matrix[0][1] ||
display_matrix[1][0] || display_matrix[1][1] != 65536 ||
display_matrix[2][0] || display_matrix[2][1])) {
for (i = 0; i < 2; i++)
disp_transform[i] =
(int64_t) width * display_matrix[0][i] +
(int64_t) height * display_matrix[1][i] +
((int64_t) display_matrix[2][i] << 16);
//sample aspect ratio is new width/height divided by old width/height
st->codec->sample_aspect_ratio = av_d2q(
((double) disp_transform[0] * height) /
((double) disp_transform[1] * width), INT_MAX);
}
return 0;
}