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decklink: Correctly ensure >=16 byte alignment for the buffers we allocate

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We'll ensure at least 64 byte alignment for AVX2 but 16 byte alignment
is what is required by the decklink SDK.

Fixes https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/issues/986
This commit is contained in:
Sebastian Dröge 2019-06-20 08:59:22 +03:00 committed by Sebastian Dröge
parent 36de11520e
commit 907dc6df68
1 changed files with 30 additions and 7 deletions
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37
sys/decklink/gstdecklink.cpp
View file

@ -1036,8 +1036,11 @@ private:
if (!m_buffers) if (!m_buffers)
return; return;
while ((buf = (uint8_t *) gst_queue_array_pop_head (m_buffers))) while ((buf = (uint8_t *) gst_queue_array_pop_head (m_buffers))) {
g_free (buf - 128); uint8_t offset = *(buf - 1);
void *alloc_buf = buf - 128 + offset;
g_free (alloc_buf);
}
} }
public: public:
@ -1097,6 +1100,7 @@ public:
AllocateBuffer (uint32_t bufferSize, void **allocatedBuffer) AllocateBuffer (uint32_t bufferSize, void **allocatedBuffer)
{ {
uint8_t *buf; uint8_t *buf;
uint8_t offset = 0;
g_mutex_lock (&m_mutex); g_mutex_lock (&m_mutex);
@ -1110,8 +1114,23 @@ public:
if (!(buf = (uint8_t *) gst_queue_array_pop_head (m_buffers))) { if (!(buf = (uint8_t *) gst_queue_array_pop_head (m_buffers))) {
/* If not, alloc a new one */ /* If not, alloc a new one */
buf = (uint8_t *) g_malloc (bufferSize + 128); buf = (uint8_t *) g_malloc (bufferSize + 128);
/* The Decklink SDK requires 16 byte aligned memory at least but for us
* to work nicely let's align to 64 bytes (512 bits) as this allows
* aligned AVX2 operations for example */
if (((guintptr) buf) % 64 != 0) {
offset = ((guintptr) buf) % 64;
}
/* Write the allocation size at the very beginning. It's guaranteed by
* malloc() to be allocated aligned enough for doing this. */
*((uint32_t *) buf) = bufferSize; *((uint32_t *) buf) = bufferSize;
buf += 128;
/* Align our buffer */
buf += 128 - offset;
/* And write the alignment offset right before the buffer */
*(buf - 1) = offset;
} }
*allocatedBuffer = (void *) buf; *allocatedBuffer = (void *) buf;
@ -1119,8 +1138,10 @@ public:
* remove one of them every fifth call */ * remove one of them every fifth call */
if (gst_queue_array_get_length (m_buffers) > 0) { if (gst_queue_array_get_length (m_buffers) > 0) {
if (++m_nonEmptyCalls >= 5) { if (++m_nonEmptyCalls >= 5) {
buf = (uint8_t *) gst_queue_array_pop_head (m_buffers) - 128; buf = (uint8_t *) gst_queue_array_pop_head (m_buffers);
g_free (buf); uint8_t offset = *(buf - 1);
void *alloc_buf = buf - 128 + offset;
g_free (alloc_buf);
m_nonEmptyCalls = 0; m_nonEmptyCalls = 0;
} }
} else { } else {
@ -1137,11 +1158,13 @@ public:
g_mutex_lock (&m_mutex); g_mutex_lock (&m_mutex);
/* Put the buffer back to the pool if size matches with current pool */ /* Put the buffer back to the pool if size matches with current pool */
uint32_t size = *(uint32_t *) ((uint8_t *) buffer - 128); uint8_t offset = *(((uint8_t *) buffer) - 1);
uint8_t *alloc_buffer = ((uint8_t *) buffer) - 128 + offset;
uint32_t size = *(uint32_t *) alloc_buffer;
if (size == m_lastBufferSize) { if (size == m_lastBufferSize) {
gst_queue_array_push_tail (m_buffers, buffer); gst_queue_array_push_tail (m_buffers, buffer);
} else { } else {
g_free (((uint8_t *) buffer) - 128); g_free (alloc_buffer);
} }
g_mutex_unlock (&m_mutex); g_mutex_unlock (&m_mutex);