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@TEMPLATE encoder_tmpl.c
VP8 Scalable Frame Patterns
===========================
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
This is an example demonstrating how to control the VP8 encoder's
reference frame selection and update mechanism for video applications
that benefit from a scalable bitstream.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
Configuration
-------------
Scalable frame patterns are most useful in an error resilient context,
so error resiliency mode is enabled, as in the `error_resilient.c`
example. In addition, we want to disable automatic keyframe selection,
so we force an interval of 1000 frames.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ENC_SET_CFG2
/* Enable error resilient mode */
cfg.g_error_resilient = 1;
cfg.g_lag_in_frames = 0;
cfg.kf_mode = VPX_KF_FIXED;
/* Disable automatic keyframe placement */
cfg.kf_min_dist = cfg.kf_max_dist = 1000;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ENC_SET_CFG2
This example uses the following frame pattern (L->last_frame,
G->golden_frame, A->alt_ref_frame):
* Frame 0 Intra, use none, update L&G&A
* Frame 1 Inter, use LGA, update none
* Frame 2 Inter, use LGA, update L
* Frame 3 Inter, use LGA, update none
* Frame 4 Inter, use GA, update L&G
* Frame 5 Inter, use LGA, update none
* Frame 6 Inter, use LGA, update L
* Frame 7 Inter, use LGA, update none
* Frame 8 Inter, use A, update L&G&A
* Frame 9 Inter, use LGA, update none
* Frame 10 Inter, use LGA, update L
* Frame 11 Inter, use LGA, update none
* Frame 12 Inter, use GA, update L&G
* Frame 13 Inter, use LGA, update none
* Frame 14 Inter, use LGA, update L
* Frame 15 Inter, use LGA, update none
* ...Repeats the pattern from frame 0
Change this variable to test the 3 decodable streams case.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TWOPASS_VARS
int num_streams = 5;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TWOPASS_VARS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PER_FRAME_CFG
flags = 0;
if(num_streams == 5)
{
switch(frame_cnt % 16) {
case 0:
flags |= VPX_EFLAG_FORCE_KF;
flags |= VP8_EFLAG_FORCE_GF;
flags |= VP8_EFLAG_FORCE_ARF;
break;
case 1:
case 3:
case 5:
case 7:
case 9:
case 11:
case 13:
case 15:
flags |= VP8_EFLAG_NO_UPD_LAST;
flags |= VP8_EFLAG_NO_UPD_GF;
flags |= VP8_EFLAG_NO_UPD_ARF;
break;
case 2:
case 6:
case 10:
case 14:
break;
case 4:
flags |= VP8_EFLAG_NO_REF_LAST;
flags |= VP8_EFLAG_FORCE_GF;
break;
case 8:
flags |= VP8_EFLAG_NO_REF_LAST;
flags |= VP8_EFLAG_NO_REF_GF;
flags |= VP8_EFLAG_FORCE_GF;
flags |= VP8_EFLAG_FORCE_ARF;
break;
case 12:
flags |= VP8_EFLAG_NO_REF_LAST;
flags |= VP8_EFLAG_FORCE_GF;
break;
}
}
else
{
switch(frame_cnt % 9) {
case 0:
if(frame_cnt==0)
{
flags |= VPX_EFLAG_FORCE_KF;
}
else
{
cfg.rc_max_quantizer = 26;
cfg.rc_min_quantizer = 0;
cfg.rc_target_bitrate = 300;
flags |= VP8_EFLAG_NO_REF_LAST;
flags |= VP8_EFLAG_NO_REF_ARF;
}
flags |= VP8_EFLAG_FORCE_GF;
flags |= VP8_EFLAG_FORCE_ARF;
break;
case 1:
case 2:
case 4:
case 5:
case 7:
case 8:
cfg.rc_max_quantizer = 45;
cfg.rc_min_quantizer = 0;
cfg.rc_target_bitrate = 230;
break;
case 3:
case 6:
cfg.rc_max_quantizer = 45;
cfg.rc_min_quantizer = 0;
cfg.rc_target_bitrate = 215;
flags |= VP8_EFLAG_NO_REF_LAST;
flags |= VP8_EFLAG_FORCE_ARF;
break;
}
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PER_FRAME_CFG
Observing The Effects
---------------------
Use the `decode_with_drops` example to decode with various dropped frame
patterns. Good patterns to start with are 1/2, 3/4, 7/8, and 15/16
drops.
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