From 8621a37d9feff940be19e47344cc521adca1fca2 Mon Sep 17 00:00:00 2001
From: Stefano Sabatini <stefano.sabatini-lala@poste.it>
Date: Wed, 5 Jan 2011 14:15:11 +0000
Subject: [PATCH] In video4linux2, in the case the timebase value in ap is 0/0,
 read the timebase value already set in the driver, and set it back in the
 codec stream, rather than leaving the invalid value of 0/0.

In particular, fix ffmpeg grabbing timestamps when the timebase value
is not set through the CLI.

Originally committed as revision 26224 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 doc/indevs.texi        |  9 +++++++--
 libavdevice/avdevice.h |  2 +-
 libavdevice/v4l2.c     | 13 +++++++++++++
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/doc/indevs.texi b/doc/indevs.texi
index d34583326d..8e862ff6bc 100644
--- a/doc/indevs.texi
+++ b/doc/indevs.texi
@@ -146,6 +146,8 @@ devices and the command @file{v4l-info} for Video4Linux2 devices.
 
 If the size for the device is set to 0x0, the input device will
 try to autodetect the size to use.
+Only for the video4linux2 device, if the frame rate is set to 0/0 the
+input device will use the frame rate value already set in the driver.
 
 Video4Linux support is deprecated since Linux 2.6.30, and will be
 dropped in later versions.
@@ -153,13 +155,16 @@ dropped in later versions.
 Follow some usage examples of the video4linux devices with the ff*
 tools.
 @example
-# Grab and show the input of a video4linux device.
+# Grab and show the input of a video4linux device, frame rate is set
+# to the default of 25/1.
 ffplay -s 320x240 -f video4linux /dev/video0
 
 # Grab and show the input of a video4linux2 device, autoadjust size.
 ffplay -f video4linux2 /dev/video0
 
-# Grab and record the input of a video4linux2 device, autoadjust size.
+# Grab and record the input of a video4linux2 device, autoadjust size,
+# frame rate value defaults to 0/0 so it is read from the video4linux2
+# driver.
 ffmpeg -f video4linux2 -i /dev/video0 out.mpeg
 @end example
 
diff --git a/libavdevice/avdevice.h b/libavdevice/avdevice.h
index 9508f2277f..5c3739fdcd 100644
--- a/libavdevice/avdevice.h
+++ b/libavdevice/avdevice.h
@@ -23,7 +23,7 @@
 
 #define LIBAVDEVICE_VERSION_MAJOR 52
 #define LIBAVDEVICE_VERSION_MINOR  2
-#define LIBAVDEVICE_VERSION_MICRO  2
+#define LIBAVDEVICE_VERSION_MICRO  3
 
 #define LIBAVDEVICE_VERSION_INT AV_VERSION_INT(LIBAVDEVICE_VERSION_MAJOR, \
                                                LIBAVDEVICE_VERSION_MINOR, \
diff --git a/libavdevice/v4l2.c b/libavdevice/v4l2.c
index 54259284af..26f879a509 100644
--- a/libavdevice/v4l2.c
+++ b/libavdevice/v4l2.c
@@ -514,6 +514,19 @@ static int v4l2_set_parameters(AVFormatContext *s1, AVFormatParameters *ap)
             ap->time_base.num = tpf->numerator;
             ap->time_base.den = tpf->denominator;
         }
+    } else {
+        /* if timebase value is not set in ap, read the timebase value
+         * from the driver and set it in ap */
+        struct v4l2_streamparm streamparm = { 0 };
+        struct v4l2_fract *tpf = &streamparm.parm.capture.timeperframe;
+
+        streamparm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+        if (ioctl(s->fd, VIDIOC_G_PARM, &streamparm) != 0) {
+            av_log(s1, AV_LOG_ERROR, "ioctl(VIDIOC_G_PARM): %s\n", strerror(errno));
+            return AVERROR(errno);
+        }
+        ap->time_base.num = tpf->numerator;
+        ap->time_base.den = tpf->denominator;
     }
 
     return 0;