v4l2: use buffer PTS where available (fix #5474)

modules/access/v4l2/demux.c

@@ -566,7 +566,7 @@ static void *UserPtrThread (void *data)
 
         assert (block->p_buffer == (void *)buf.m.userptr);
         block->i_buffer = buf.length;
-        block->i_pts = block->i_dts = mdate ();
+        block->i_pts = block->i_dts = GetBufferPTS (&buf);
         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);
@@ -611,7 +611,6 @@ static void *MmapThread (void *data)
             block_t *block = GrabVideo (VLC_OBJECT(demux), fd, sys->bufv);
             if (block != NULL)
             {
-                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);

modules/access/v4l2/v4l2.h

@@ -55,6 +55,7 @@ int StartUserPtr (vlc_object_t *, int);
 struct buffer_t *StartMmap (vlc_object_t *, int, uint32_t *);
 void StopMmap (int, struct buffer_t *, uint32_t);
 
+mtime_t GetBufferPTS (const struct v4l2_buffer *);
 block_t* GrabVideo (vlc_object_t *, int, const struct buffer_t *);
 
 #ifdef ZVBI_COMPILED

modules/access/v4l2/video.c

@@ -28,6 +28,7 @@
 # include "config.h"
 #endif
 
+#include <assert.h>
 #include <errno.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
@@ -513,6 +514,24 @@ int SetupFormat (vlc_object_t *obj, int fd, uint32_t fourcc,
     return 0;
 }
 
+mtime_t GetBufferPTS (const struct v4l2_buffer *buf)
+{
+    mtime_t pts;
+
+    switch (buf->flags & V4L2_BUF_FLAG_TIMESTAMP_MASK)
+    {
+        case V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC:
+            pts = (buf->timestamp.tv_sec * CLOCK_FREQ)
+                 + buf->timestamp.tv_usec;
+            static_assert (CLOCK_FREQ == 1000000, "Clock unit mismatch");
+            break;
+        case V4L2_BUF_FLAG_TIMESTAMP_UNKNOWN:
+        default:
+            pts = mdate ();
+            break;
+    }
+    return pts;
+}
 
 /*****************************************************************************
  * GrabVideo: Grab a video frame
@@ -545,6 +564,7 @@ block_t *GrabVideo (vlc_object_t *demux, int fd,
     block_t *block = block_Alloc (buf.bytesused);
     if (unlikely(block == NULL))
         return NULL;
+    block->i_pts = block->i_dts = GetBufferPTS (&buf);
     memcpy (block->p_buffer, bufv[buf.index].start, buf.bytesused);
 
     /* Unlock */