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codecparsers_h264: add gst_h264_video_calculate_framerate()

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Add a new function to calculate video stream framerate which rely on
SPS, slice header and pic timing using formula:

         time_scale                1                         1
fps = -----------------  x  ---------------  x  ------------------------
      num_units_in_tick     DeltaTfiDivisor     (field_pic_flag ? 2 : 1)

See section E2.1 of H264 specification for definition of variables.

https://bugzilla.gnome.org/show_bug.cgi?id=723352
This commit is contained in:
Aurélien Zanelli 2014-05-19 17:43:54 +02:00 committed by Sebastian Dröge
parent 746d021d70
commit 753701bf68
3 changed files with 79 additions and 0 deletions
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1
docs/libs/gst-plugins-bad-libs-sections.txt
View file

@ -44,6 +44,7 @@ gst_h264_video_quant_matrix_8x8_get_zigzag_from_raster
gst_h264_video_quant_matrix_8x8_get_raster_from_zigzag
gst_h264_video_quant_matrix_4x4_get_zigzag_from_raster
gst_h264_video_quant_matrix_4x4_get_raster_from_zigzag
gst_h264_video_calculate_framerate
<SUBSECTION Standard>
<SUBSECTION Private>
</SECTION>

75
gst-libs/gst/codecparsers/gsth264parser.c
View file

@ -1875,3 +1875,78 @@ gst_h264_video_quant_matrix_4x4_get_raster_from_zigzag (guint8 out_quant[16],
for (i = 0; i < 16; i++)
out_quant[zigzag_4x4[i]] = quant[i];
}
/**
* gst_h264_video_calculate_framerate:
* @sps: Current Sequence Parameter Set
* @field_pic_flag: Current @field_pic_flag, obtained from latest slice header
* @pic_struct: @pic_struct value if available, 0 otherwise
* @fps_num: (out): The resulting fps numerator
* @fps_den: (out): The resulting fps denominator
*
* Calculate framerate of a video sequence using @sps VUI information,
* @field_pic_flag from a slice header and @pic_struct from #GstH264PicTiming SEI
* message.
*
* If framerate is variable or can't be determined, @fps_num will be set to 0
* and @fps_den to 1.
*/
void
gst_h264_video_calculate_framerate (const GstH264SPS * sps,
guint field_pic_flag, guint pic_struct, gint * fps_num, gint * fps_den)
{
gint num = 0;
gint den = 1;
/* To calculate framerate, we use this formula:
* time_scale 1 1
* fps = ----------------- x --------------- x ------------------------
* num_units_in_tick DeltaTfiDivisor (field_pic_flag ? 2 : 1)
*
* See H264 specification E2.1 for more details.
*/
if (sps) {
if (sps->vui_parameters_present_flag) {
const GstH264VUIParams *vui = &sps->vui_parameters;
if (vui->timing_info_present_flag && vui->fixed_frame_rate_flag) {
int delta_tfi_divisor = 1;
num = vui->time_scale;
den = vui->num_units_in_tick;
if (vui->pic_struct_present_flag) {
switch (pic_struct) {
case 1:
case 2:
delta_tfi_divisor = 1;
break;
case 0:
case 3:
case 4:
delta_tfi_divisor = 2;
break;
case 5:
case 6:
delta_tfi_divisor = 3;
break;
case 7:
delta_tfi_divisor = 4;
break;
case 8:
delta_tfi_divisor = 6;
break;
}
} else {
delta_tfi_divisor = field_pic_flag ? 1 : 2;
}
den *= delta_tfi_divisor;
/* Picture is two fields ? */
den *= (field_pic_flag ? 2 : 1);
}
}
}
*fps_num = num;
*fps_den = den;
}

3
gst-libs/gst/codecparsers/gsth264parser.h
View file

@ -781,6 +781,9 @@ void gst_h264_video_quant_matrix_4x4_get_zigzag_from_raster (guint8 out_quant
void gst_h264_video_quant_matrix_4x4_get_raster_from_zigzag (guint8 out_quant[16],
const guint8 quant[16]);
void gst_h264_video_calculate_framerate (const GstH264SPS * sps, guint field_pic_flag,
guint pic_struct, gint * fps_num, gint * fps_den);
G_END_DECLS
#endif