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Rewrite buffer patching logic to avoid leaking if the first NALU has an unexpected offset

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This commit is contained in:
Cameron Gutman
2022-09-28 17:42:48 -05:00
parent c21f638399
commit 2ae79c5827
1 changed files with 49 additions and 84 deletions
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133
Limelight/Stream/VideoDecoderRenderer.m
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@@ -156,82 +156,37 @@ int DrSubmitDecodeUnit(PDECODE_UNIT decodeUnit);
}
}
- (void)updateBufferForRange:(CMBlockBufferRef)existingBuffer data:(unsigned char *)data offset:(int)offset length:(int)nalLength
- (void)updateBufferForRange:(CMBlockBufferRef)frameBuffer dataBlock:(CMBlockBufferRef)dataBuffer offset:(int)offset length:(int)nalLength
{
OSStatus status;
size_t oldOffset = CMBlockBufferGetDataLength(existingBuffer);
size_t oldOffset = CMBlockBufferGetDataLength(frameBuffer);
// If we're the first NALU in frame, enqueue this buffer to the memory block
// so it can handle freeing it when the block buffer is destroyed
if (offset == 0 || offset == 1) {
int dataLength = nalLength - NALU_START_PREFIX_SIZE;
// If we get here with offset 0, this is a 3 byte Annex B prefix. This means
// we don't have enough space to do an in-place Annex B -> AVCC fixup.
// To allow the in-place fixup to work, prepend a 1 byte buffer.
if (offset == 0) {
status = CMBlockBufferAppendMemoryBlock(existingBuffer, NULL, 1,
kCFAllocatorDefault,
NULL, 0, 1, 0);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferAppendMemoryBlock failed: %d", (int)status);
return;
}
}
// Pass the real buffer pointer directly (no offset)
// This will give it to the block buffer to free when it's released.
// All further calls to CMBlockBufferAppendMemoryBlock will do so
// at an offset and will not be asking the buffer to be freed.
status = CMBlockBufferAppendMemoryBlock(existingBuffer, data,
nalLength + offset,
kCFAllocatorDefault,
NULL, 0, nalLength + offset, 0);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferReplaceDataBytes failed: %d", (int)status);
return;
}
// Write the length prefix to existing buffer
const uint8_t lengthBytes[] = {(uint8_t)(dataLength >> 24), (uint8_t)(dataLength >> 16),
(uint8_t)(dataLength >> 8), (uint8_t)dataLength};
status = CMBlockBufferReplaceDataBytes(lengthBytes, existingBuffer,
oldOffset, NAL_LENGTH_PREFIX_SIZE);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferReplaceDataBytes failed: %d", (int)status);
return;
}
} else {
// Append a 4 byte buffer to this block for the length prefix
status = CMBlockBufferAppendMemoryBlock(existingBuffer, NULL,
NAL_LENGTH_PREFIX_SIZE,
kCFAllocatorDefault, NULL, 0,
NAL_LENGTH_PREFIX_SIZE, 0);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferAppendMemoryBlock failed: %d", (int)status);
return;
}
// Write the length prefix to the new buffer
int dataLength = nalLength - NALU_START_PREFIX_SIZE;
const uint8_t lengthBytes[] = {(uint8_t)(dataLength >> 24), (uint8_t)(dataLength >> 16),
(uint8_t)(dataLength >> 8), (uint8_t)dataLength};
status = CMBlockBufferReplaceDataBytes(lengthBytes, existingBuffer,
oldOffset, NAL_LENGTH_PREFIX_SIZE);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferReplaceDataBytes failed: %d", (int)status);
return;
}
// Attach the buffer by reference to the block buffer
status = CMBlockBufferAppendMemoryBlock(existingBuffer, &data[offset+NALU_START_PREFIX_SIZE],
dataLength,
kCFAllocatorNull, // Don't deallocate data on free
NULL, 0, dataLength, 0);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferReplaceDataBytes failed: %d", (int)status);
return;
}
// Append a 4 byte buffer to the frame block for the length prefix
status = CMBlockBufferAppendMemoryBlock(frameBuffer, NULL,
NAL_LENGTH_PREFIX_SIZE,
kCFAllocatorDefault, NULL, 0,
NAL_LENGTH_PREFIX_SIZE, 0);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferAppendMemoryBlock failed: %d", (int)status);
return;
}
// Write the length prefix to the new buffer
const int dataLength = nalLength - NALU_START_PREFIX_SIZE;
const uint8_t lengthBytes[] = {(uint8_t)(dataLength >> 24), (uint8_t)(dataLength >> 16),
(uint8_t)(dataLength >> 8), (uint8_t)dataLength};
status = CMBlockBufferReplaceDataBytes(lengthBytes, frameBuffer,
oldOffset, NAL_LENGTH_PREFIX_SIZE);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferReplaceDataBytes failed: %d", (int)status);
return;
}
// Attach the data buffer to the frame buffer by reference
status = CMBlockBufferAppendBufferReference(frameBuffer, dataBuffer, offset + NALU_START_PREFIX_SIZE, dataLength, 0);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferAppendBufferReference failed: %d", (int)status);
return;
}
}
@@ -335,12 +290,22 @@ int DrSubmitDecodeUnit(PDECODE_UNIT decodeUnit);
}
// Now we're decoding actual frame data here
CMBlockBufferRef blockBuffer;
CMBlockBufferRef frameBlockBuffer;
CMBlockBufferRef dataBlockBuffer;
status = CMBlockBufferCreateEmpty(NULL, 0, 0, &blockBuffer);
status = CMBlockBufferCreateWithMemoryBlock(NULL, data, length, kCFAllocatorDefault, NULL, 0, length, 0, &dataBlockBuffer);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferCreateWithMemoryBlock failed: %d", (int)status);
free(data);
return DR_NEED_IDR;
}
// From now on, CMBlockBuffer owns the data pointer and will free it when it's dereferenced
status = CMBlockBufferCreateEmpty(NULL, 0, 0, &frameBlockBuffer);
if (status != noErr) {
Log(LOG_E, @"CMBlockBufferCreateEmpty failed: %d", (int)status);
free(data);
CFRelease(dataBlockBuffer);
return DR_NEED_IDR;
}
@@ -351,7 +316,7 @@ int DrSubmitDecodeUnit(PDECODE_UNIT decodeUnit);
// It's the start of a new NALU
if (lastOffset != -1) {
// We've seen a start before this so enqueue that NALU
[self updateBufferForRange:blockBuffer data:data offset:lastOffset length:i - lastOffset];
[self updateBufferForRange:frameBlockBuffer dataBlock:dataBlockBuffer offset:lastOffset length:i - lastOffset];
}
lastOffset = i;
@@ -360,22 +325,21 @@ int DrSubmitDecodeUnit(PDECODE_UNIT decodeUnit);
if (lastOffset != -1) {
// Enqueue the remaining data
[self updateBufferForRange:blockBuffer data:data offset:lastOffset length:length - lastOffset];
[self updateBufferForRange:frameBlockBuffer dataBlock:dataBlockBuffer offset:lastOffset length:length - lastOffset];
}
// From now on, CMBlockBuffer owns the data pointer and will free it when it's dereferenced
CMSampleBufferRef sampleBuffer;
status = CMSampleBufferCreate(kCFAllocatorDefault,
blockBuffer,
frameBlockBuffer,
true, NULL,
NULL, formatDesc, 1, 0,
NULL, 0, NULL,
&sampleBuffer);
if (status != noErr) {
Log(LOG_E, @"CMSampleBufferCreate failed: %d", (int)status);
CFRelease(blockBuffer);
CFRelease(dataBlockBuffer);
CFRelease(frameBlockBuffer);
return DR_NEED_IDR;
}
@@ -407,7 +371,8 @@ int DrSubmitDecodeUnit(PDECODE_UNIT decodeUnit);
}
// Dereference the buffers
CFRelease(blockBuffer);
CFRelease(dataBlockBuffer);
CFRelease(frameBlockBuffer);
CFRelease(sampleBuffer);
return DR_OK;