lavf: add av_guess_frame_sample_aspect_ratio function

Guesses the sample aspect ratio of a frame, based on both the stream and the
frame aspect ratio.

Since the frame aspect ratio is set by the codec but the stream aspect ratio
is set by the demuxer, these two may not be equal. This function tries to
return the value that you should use if you would like to display the frame.

Basic logic is to use the stream aspect ratio if it is set to something sane
otherwise use the frame aspect ratio. This way a container setting, which is
usually easy to modify can override the coded value in the frames.

Signed-off-by: Marton Balint <cus@passwd.hu>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

diff --git a/doc/APIchanges b/doc/APIchanges
index 57537228b11a3730a6f9a490aa128d446dfdd282..2d25d491149240b937b420c4a26766052d74d6cf 100644 (file)
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -15,6 +15,9 @@ libavutil:     2011-04-18
 
 API changes, most recent first:
 
+2012-05-07 - xxxxxxx - lavf 54.5.100
+  Add av_guess_sample_aspect_ratio() function.
+
 2012-04-20 - xxxxxxx - lavfi 2.70.100
   Add avfilter_unref_bufferp() to avfilter.h.
 

diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index ce9d70a8ad7d52d528ba43b4e39477bbda0c95a0..9f520e721589cb4bba8e9295614d032c25bfd5c3 100644 (file)
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1911,6 +1911,26 @@ const struct AVCodecTag *avformat_get_riff_video_tags(void);
  * @return the table mapping RIFF FourCCs for audio to CodecID.
  */
 const struct AVCodecTag *avformat_get_riff_audio_tags(void);
+
+/**
+ * Guesses the sample aspect ratio of a frame, based on both the stream and the
+ * frame aspect ratio.
+ *
+ * Since the frame aspect ratio is set by the codec but the stream aspect ratio
+ * is set by the demuxer, these two may not be equal. This function tries to
+ * return the value that you should use if you would like to display the frame.
+ *
+ * Basic logic is to use the stream aspect ratio if it is set to something sane
+ * otherwise use the frame aspect ratio. This way a container setting, which is
+ * usually easy to modify can override the coded value in the frames.
+ *
+ * @param format the format context which the stream is part of
+ * @param stream the stream which the frame is part of
+ * @param frame the frame with the aspect ratio to be determined
+ * @return the guessed (valid) sample_aspect_ratio, 0/1 if no idea
+ */
+AVRational av_guess_sample_aspect_ratio(AVFormatContext *format, AVStream *stream, AVFrame *frame);
+
 /**
  * @}
  */

diff --git a/libavformat/utils.c b/libavformat/utils.c
index d19e4270bfe7f4131bc9e84a6d3426f2689d4295..c0f6d45c2af73569c9ddebd02e26b30dc1c766e1 100644 (file)
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -4414,3 +4414,25 @@ const struct AVCodecTag *avformat_get_riff_audio_tags(void)
 {
     return ff_codec_wav_tags;
 }
+
+AVRational av_guess_sample_aspect_ratio(AVFormatContext *format, AVStream *stream, AVFrame *frame)
+{
+    AVRational undef = {0, 1};
+    AVRational stream_sample_aspect_ratio = stream ? stream->sample_aspect_ratio : undef;
+    AVRational frame_sample_aspect_ratio  = frame  ? frame->sample_aspect_ratio  : undef;
+
+    av_reduce(&stream_sample_aspect_ratio.num, &stream_sample_aspect_ratio.den,
+               stream_sample_aspect_ratio.num,  stream_sample_aspect_ratio.den, INT_MAX);
+    if (stream_sample_aspect_ratio.num <= 0 || stream_sample_aspect_ratio.den <= 0)
+        stream_sample_aspect_ratio = undef;
+
+    av_reduce(&frame_sample_aspect_ratio.num, &frame_sample_aspect_ratio.den,
+               frame_sample_aspect_ratio.num,  frame_sample_aspect_ratio.den, INT_MAX);
+    if (frame_sample_aspect_ratio.num <= 0 || frame_sample_aspect_ratio.den <= 0)
+        frame_sample_aspect_ratio = undef;
+
+    if (stream_sample_aspect_ratio.num)
+        return stream_sample_aspect_ratio;
+    else
+        return frame_sample_aspect_ratio;
+}

diff --git a/libavformat/version.h b/libavformat/version.h
index a3143c395fbe378a48d7845fa51e7dd61fee0e54..17f8b161c1a46147523504127d49b884f7fc5eef 100644 (file)
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -30,7 +30,7 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR 54
-#define LIBAVFORMAT_VERSION_MINOR  4
+#define LIBAVFORMAT_VERSION_MINOR  5
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \