jyapayne/moonlight-common-c
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Fix race condition that could result in loss of NALUs in an IDR frame

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Unfortunately, this was a design flaw in the way we handled IDR frames
NALUs. Because we split them all up and handled them as separate
"frames" in the system, some of them could be discarded due to a
video decode unit overflow, for example, and cause the decoder to get
confused due to receiving an SPS without a following PPS.

To address this, NALUs in the IDR frame are always delivered together
as one frame. The SPS, PPS, and VPS are now in separate buffers in
the IDR frame's buffer list and tagged as such with the new buffer
type field. The IDR frames themselves have a new frame type field
which marks them as special frames that clients may need to process
in a special way.

This will likely be a breaking change for your clients!
This commit is contained in:
Cameron Gutman 2017-11-13 10:15:43 -08:00
commit 1c386a8987
2 changed files with 73 additions and 9 deletions
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59
src/VideoDepacketizer.c
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@ -231,6 +231,14 @@ static void reassembleFrame(int frameNumber) {
qdu->decodeUnit.frameNumber = frameNumber;
qdu->decodeUnit.receiveTimeMs = firstPacketReceiveTime;
// IDR frames will have leading CSD buffers
if (nalChainHead->bufferType != BUFFER_TYPE_PICDATA) {
qdu->decodeUnit.frameType = FRAME_TYPE_IDR;
}
else {
qdu->decodeUnit.frameType = FRAME_TYPE_PFRAME;
}
nalChainHead = NULL;
nalChainDataLength = 0;
@ -274,7 +282,43 @@ static void reassembleFrame(int frameNumber) {
}
}
static void queueFragment(char*data, int offset, int length) {
#define AVC_NAL_TYPE_SPS 0x67
#define AVC_NAL_TYPE_PPS 0x68
#define HEVC_NAL_TYPE_VPS 0x40
#define HEVC_NAL_TYPE_SPS 0x42
#define HEVC_NAL_TYPE_PPS 0x44
static int getBufferFlags(char* data, int length) {
BUFFER_DESC buffer;
BUFFER_DESC candidate;
buffer.data = data;
buffer.length = (unsigned int)length;
buffer.offset = 0;
if (!getSpecialSeq(&buffer, &candidate) || !isSeqFrameStart(&candidate)) {
return BUFFER_TYPE_PICDATA;
}
switch (candidate.data[candidate.offset + candidate.length]) {
case AVC_NAL_TYPE_SPS:
case HEVC_NAL_TYPE_SPS:
return BUFFER_TYPE_SPS;
case AVC_NAL_TYPE_PPS:
case HEVC_NAL_TYPE_PPS:
return BUFFER_TYPE_PPS;
case HEVC_NAL_TYPE_VPS:
return BUFFER_TYPE_VPS;
default:
return BUFFER_TYPE_PICDATA;
}
}
static void queueFragment(char* data, int offset, int length) {
PLENTRY entry = (PLENTRY)malloc(sizeof(*entry) + length);
if (entry != NULL) {
entry->next = NULL;
@ -283,6 +327,8 @@ static void queueFragment(char*data, int offset, int length) {
memcpy(entry->data, &data[offset], entry->length);
entry->bufferType = getBufferFlags(entry->data, entry->length);
nalChainDataLength += entry->length;
if (nalChainHead == NULL) {
@ -305,6 +351,9 @@ static void processRtpPayloadSlow(PNV_VIDEO_PACKET videoPacket, PBUFFER_DESC cur
BUFFER_DESC specialSeq;
int decodingVideo = 0;
// We should not have any NALUs when processing the first packet in an IDR frame
LC_ASSERT(nalChainHead == NULL);
while (currentPos->length != 0) {
int start = currentPos->offset;
@ -317,9 +366,6 @@ static void processRtpPayloadSlow(PNV_VIDEO_PACKET videoPacket, PBUFFER_DESC cur
// Now we're working on a frame
decodingFrame = 1;
// Reassemble any pending frame
reassembleFrame(videoPacket->frameIndex);
if (isSeqReferenceFrameStart(&specialSeq)) {
// No longer waiting for an IDR frame
waitingForIdrFrame = 0;
@ -334,11 +380,6 @@ static void processRtpPayloadSlow(PNV_VIDEO_PACKET videoPacket, PBUFFER_DESC cur
currentPos->offset += specialSeq.length;
}
else {
// Check if this is padding after a full frame
if (decodingVideo && isSeqPadding(currentPos)) {
reassembleFrame(videoPacket->frameIndex);
}
// Not decoding video
decodingVideo = 0;