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obs-vth264: Manually mark priority bits for VideoToolbox frames

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Reland of 30d29618, except actually tested this time.

The VideoToolbox encoder gives I-frames and P-frames a priority of 1,
but the RTMP output code expects I-frames to have priority 3 and
P-frames to have priority 2.

30d29618 changed the priority of all frames that aren't I-frames, but
that included B-frames as well as P-frames. B-frames are given a
priority of 0 by VideoToolbox and changing that priority causes
artifacts for reasons I don't understand. So ignore the B-frames by
ignoring slice packets with priority 0.
This commit is contained in:
Theodore Dubois
2020-02-16 12:28:50 -08:00
parent d13f204488
commit 5d3fbc15ae
1 changed files with 34 additions and 0 deletions
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34
plugins/mac-vth264/encoder.c
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@@ -1,5 +1,6 @@
#include <obs-module.h>
#include <util/darray.h>
#include <obs-avc.h>
#include <CoreFoundation/CoreFoundation.h>
#include <VideoToolbox/VideoToolbox.h>
@@ -671,6 +672,8 @@ static bool is_sample_keyframe(CMSampleBufferRef buffer)
static bool parse_sample(struct vt_h264_encoder *enc, CMSampleBufferRef buffer,
struct encoder_packet *packet, CMTime off)
{
int type;
CMTime pts = CMSampleBufferGetPresentationTimeStamp(buffer);
CMTime dts = CMSampleBufferGetDecodeTimeStamp(buffer);
@@ -703,6 +706,37 @@ static bool parse_sample(struct vt_h264_encoder *enc, CMSampleBufferRef buffer,
packet->size = enc->packet_data.num;
packet->keyframe = keyframe;
// VideoToolbox produces packets with priority lower than the RTMP code
// expects, which causes it to be unable to recover from frame drops.
// Fix this by manually adjusting the priority.
uint8_t *start = enc->packet_data.array;
uint8_t *end = start + enc->packet_data.num;
start = (uint8_t *)obs_avc_find_startcode(start, end);
while (true) {
while (start < end && !*(start++))
;
if (start == end)
break;
type = start[0] & 0x1F;
if (type == OBS_NAL_SLICE_IDR || type == OBS_NAL_SLICE) {
uint8_t prev_type = (start[0] >> 5) & 0x3;
start[0] &= ~(3 << 5);
if (type == OBS_NAL_SLICE_IDR)
start[0] |= OBS_NAL_PRIORITY_HIGHEST << 5;
else if (type == OBS_NAL_SLICE &&
prev_type != OBS_NAL_PRIORITY_DISPOSABLE)
start[0] |= OBS_NAL_PRIORITY_HIGH << 5;
else
start[0] |= prev_type << 5;
}
start = (uint8_t *)obs_avc_find_startcode(start, end);
}
CFRelease(buffer);
return true;