[vlc-commits] v4l2: reintroduce user pointer mode, now with zero copy
Rémi Denis-Courmont
git at videolan.org
Fri Apr 13 19:39:59 CEST 2012
vlc | branch: master | Rémi Denis-Courmont <remi at remlab.net> | Fri Apr 13 20:38:17 2012 +0300| [648cfc2e344f9993461d4272638d638b5b41027c] | committer: Rémi Denis-Courmont
v4l2: reintroduce user pointer mode, now with zero copy
This is negotiated automatically. Unfortunately, it will fail in most
cases (gspca might support it, UVC only supports it in future kernel
version 3.4, and libv4l does not support it anyway).
> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=648cfc2e344f9993461d4272638d638b5b41027c
---
modules/access/v4l2/demux.c | 122 +++++++++++++++++++++++++++++++++++++++---
modules/access/v4l2/v4l2.h | 1 +
modules/access/v4l2/video.c | 24 ++++++++
3 files changed, 138 insertions(+), 9 deletions(-)
diff --git a/modules/access/v4l2/demux.c b/modules/access/v4l2/demux.c
index dcebbb9..889a949 100644
--- a/modules/access/v4l2/demux.c
+++ b/modules/access/v4l2/demux.c
@@ -58,7 +58,8 @@ struct demux_sys_t
vlc_v4l2_ctrl_t *controls;
};
-static void *StreamThread (void *);
+static void *UserPtrThread (void *);
+static void *MmapThread (void *);
static void *ReadThread (void *);
static int DemuxControl( demux_t *, int, va_list );
static int InitVideo (demux_t *, int);
@@ -439,21 +440,40 @@ static int InitVideo (demux_t *demux, int fd)
void *(*entry) (void *);
if (caps & V4L2_CAP_STREAMING)
{
- sys->bufc = 4;
- sys->bufv = StartMmap (VLC_OBJECT(demux), fd, &sys->bufc);
- if (sys->bufv == NULL)
- return -1;
- entry = StreamThread;
+ if (StartUserPtr (VLC_OBJECT(demux), fd) == 0)
+ {
+ /* In principles, mmap() will pad the length to a multiple of the
+ * page size, so there is no need to care. Nevertheless with the
+ * page size, block->i_size can be set optimally. */
+ const long pagemask = sysconf (_SC_PAGE_SIZE) - 1;
+
+ sys->blocksize = (fmt.fmt.pix.sizeimage + pagemask) & ~pagemask;
+ sys->bufv = NULL;
+ entry = UserPtrThread;
+ msg_Dbg (demux, "streaming with %"PRIu32"-bytes user buffers",
+ sys->blocksize);
+ }
+ else /* fall back to memory map */
+ {
+ sys->bufc = 4;
+ sys->bufv = StartMmap (VLC_OBJECT(demux), fd, &sys->bufc);
+ if (sys->bufv == NULL)
+ return -1;
+ entry = MmapThread;
+ msg_Dbg (demux, "streaming with %"PRIu32" memory-mapped buffers",
+ sys->bufc);
+ }
}
else if (caps & V4L2_CAP_READWRITE)
{
- sys->bufv = NULL;
sys->blocksize = fmt.fmt.pix.sizeimage;
+ sys->bufv = NULL;
entry = ReadThread;
+ msg_Dbg (demux, "reading %zu bytes at a time", sys->blocksize);
}
else
{
- msg_Err (demux, "no supported I/O method");
+ msg_Err (demux, "no supported capture method");
return -1;
}
@@ -480,7 +500,91 @@ void DemuxClose( vlc_object_t *obj )
free( sys );
}
-static void *StreamThread (void *data)
+/** Allocates and queue a user buffer using mmap(). */
+static block_t *UserPtrQueue (vlc_object_t *obj, int fd, size_t length)
+{
+ void *ptr = mmap (NULL, length, PROT_READ | PROT_WRITE,
+ MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+ if (ptr == MAP_FAILED)
+ {
+ msg_Err (obj, "cannot allocate %zu-bytes buffer: %m", length);
+ return NULL;
+ }
+
+ block_t *block = block_mmap_Alloc (ptr, length);
+ if (unlikely(block == NULL))
+ {
+ munmap (ptr, length);
+ return NULL;
+ }
+
+ struct v4l2_buffer buf = {
+ .type = V4L2_BUF_TYPE_VIDEO_CAPTURE,
+ .memory = V4L2_MEMORY_USERPTR,
+ .m = {
+ .userptr = (uintptr_t)ptr,
+ },
+ .length = length,
+ };
+
+ if (v4l2_ioctl (fd, VIDIOC_QBUF, &buf) < 0)
+ {
+ msg_Err (obj, "cannot queue buffer: %m");
+ block_Release (block);
+ return NULL;
+ }
+ return block;
+}
+
+static void *UserPtrThread (void *data)
+{
+ demux_t *demux = data;
+ demux_sys_t *sys = demux->p_sys;
+ int fd = sys->fd;
+ struct pollfd ufd[1];
+
+ ufd[0].fd = fd;
+ ufd[0].events = POLLIN;
+
+ int canc = vlc_savecancel ();
+ for (;;)
+ {
+ struct v4l2_buffer buf = {
+ .type = V4L2_BUF_TYPE_VIDEO_CAPTURE,
+ .memory = V4L2_MEMORY_USERPTR,
+ };
+ block_t *block = UserPtrQueue (VLC_OBJECT(demux), fd, sys->blocksize);
+ if (block == NULL)
+ break;
+
+ /* Wait for data */
+ vlc_restorecancel (canc);
+ block_cleanup_push (block);
+ while (poll (ufd, 1, -1) == -1)
+ if (errno != EINTR)
+ msg_Err (demux, "poll error: %m");
+ vlc_cleanup_pop ();
+ canc = vlc_savecancel ();
+
+ if (v4l2_ioctl (fd, VIDIOC_DQBUF, &buf) < 0)
+ {
+ msg_Err (demux, "cannot dequeue buffer: %m");
+ block_Release (block);
+ continue;
+ }
+
+ assert (block->p_buffer == (void *)buf.m.userptr);
+ block->i_buffer = buf.length;
+ block->i_pts = block->i_dts = mdate ();
+ block->i_flags |= sys->block_flags;
+ es_out_Control (demux->out, ES_OUT_SET_PCR, block->i_pts);
+ es_out_Send (demux->out, sys->es, block);
+ }
+ vlc_restorecancel (canc); /* <- hmm, this is purely cosmetic */
+ return NULL;
+}
+
+static void *MmapThread (void *data)
{
demux_t *demux = data;
demux_sys_t *sys = demux->p_sys;
diff --git a/modules/access/v4l2/v4l2.h b/modules/access/v4l2/v4l2.h
index 459b312..8db5b6a 100644
--- a/modules/access/v4l2/v4l2.h
+++ b/modules/access/v4l2/v4l2.h
@@ -88,6 +88,7 @@ int SetupFormat (vlc_object_t *, int, uint32_t,
#define SetupFormat(o,fd,fcc,fmt,p) \
SetupFormat(VLC_OBJECT(o),fd,fcc,fmt,p)
+int StartUserPtr (vlc_object_t *, int);
struct buffer_t *StartMmap (vlc_object_t *, int, uint32_t *);
void StopMmap (int, struct buffer_t *, uint32_t);
diff --git a/modules/access/v4l2/video.c b/modules/access/v4l2/video.c
index b0f4f8a..2e669dd 100644
--- a/modules/access/v4l2/video.c
+++ b/modules/access/v4l2/video.c
@@ -559,6 +559,30 @@ block_t *GrabVideo (vlc_object_t *demux, int fd,
}
/**
+ * Allocates user pointer buffers, and start streaming.
+ */
+int StartUserPtr (vlc_object_t *obj, int fd)
+{
+ struct v4l2_requestbuffers reqbuf = {
+ .type = V4L2_BUF_TYPE_VIDEO_CAPTURE,
+ .memory = V4L2_MEMORY_USERPTR,
+ .count = 2,
+ };
+
+ if (v4l2_ioctl (fd, VIDIOC_REQBUFS, &reqbuf) < 0)
+ {
+ msg_Dbg (obj, "cannot reserve user buffers: %m");
+ return -1;
+ }
+ if (v4l2_ioctl (fd, VIDIOC_STREAMON, &reqbuf.type) < 0)
+ {
+ msg_Err (obj, "cannot start streaming: %m");
+ return -1;
+ }
+ return 0;
+}
+
+/**
* Allocates memory-mapped buffers, queues them and start streaming.
* @param n requested buffers count [IN], allocated buffers count [OUT]
* @return array of allocated buffers (use free()), or NULL on error.
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