VideoProperties: fixed getGopSize method

Clement Champetier · Clement Champetier · commit a86ec98f2bb2 · 2016-05-13T11:19:48.000+02:00
* AVCodecContext->gop_size is unused when decode according to the ffmpeg documentation: https://ffmpeg.org/doxygen/2.8/structAVCodecContext.html#a9b6b3f1fcbdcc2ad9f4dbb4370496e38 * So compute this info when analyseGopStructure, and store it inside the VideoProperties class. * Because the gop size could be used inside getBitRate() method, throw a runtime exception before using it.
diff --git a/src/AvTranscoder/properties/VideoProperties.cpp b/src/AvTranscoder/properties/VideoProperties.cpp
@@ -24,6 +24,7 @@ VideoProperties::VideoProperties(const FormatContext& formatContext, const size_
     , _pixelProperties()
     , _isInterlaced(false)
     , _isTopFieldFirst(false)
+    , _gopSize(0)
     , _gopStructure()
     , _firstGopTimeCode(-1)
 {
@@ -332,6 +333,10 @@ size_t VideoProperties::getBitRate() const
     if(!_codecContext->width || !_codecContext->height)
         throw std::runtime_error("cannot compute bit rate: invalid frame size");
 
+    // Needed to get the gop size
+    if(_levelAnalysis < eAnalyseLevelFirstGop)
+        throw std::runtime_error("cannot compute bit rate: need to get info from the first gop (see eAnalyseLevelFirstGop)");
+
     // discard no frame type when decode
     _codecContext->skip_frame = AVDISCARD_NONE;
 
@@ -413,13 +418,6 @@ size_t VideoProperties::getHeight() const
     return _codecContext->height;
 }
 
-size_t VideoProperties::getGopSize() const
-{
-    if(!_codecContext)
-        throw std::runtime_error("unknown codec context");
-    return _codecContext->gop_size;
-}
-
 size_t VideoProperties::getDtgActiveFormat() const
 {
     if(!_codecContext)
@@ -487,7 +485,8 @@ void VideoProperties::analyseGopStructure(IProgress& progress)
             Frame frame;
             size_t count = 0;
             int gotFrame = 0;
-            bool stopAnalyse = false;
+            int positionOfFirstKeyFrame = -1;
+            int positionOfLastKeyFrame = -1;
 
             while(!av_read_frame(const_cast<AVFormatContext*>(_formatContext), &pkt))
             {
@@ -497,25 +496,34 @@ void VideoProperties::analyseGopStructure(IProgress& progress)
                     if(gotFrame)
                     {
                         AVFrame& avFrame = frame.getAVFrame();
+
                         _gopStructure.push_back(
                             std::make_pair(av_get_picture_type_char(avFrame.pict_type), avFrame.key_frame));
                         _isInterlaced = avFrame.interlaced_frame;
                         _isTopFieldFirst = avFrame.top_field_first;
+                        if(avFrame.pict_type == AV_PICTURE_TYPE_I)
+                        {
+                            if(positionOfFirstKeyFrame == -1)
+                                positionOfFirstKeyFrame = count;
+                            else
+                                positionOfLastKeyFrame = count;
+                        }
+
                         ++count;
-                        if(progress.progress(count, getGopSize()) == eJobStatusCancel)
-                            stopAnalyse = true;
                     }
                 }
-
                 av_free_packet(&pkt);
 
-                if(getGopSize() == count)
+                // If the first 2 key frames are found
+                if(positionOfFirstKeyFrame != -1 && positionOfLastKeyFrame != -1)
                 {
-                    stopAnalyse = true;
-                }
-
-                if(stopAnalyse)
+                    // Set gop size as distance between these 2 key frames
+                    _gopSize = positionOfLastKeyFrame - positionOfFirstKeyFrame;
+                    // Update gop structure to keep only one gop
+                    while(_gopStructure.size() > _gopSize)
+                        _gopStructure.pop_back();
                     break;
+                }
             }
 
             // Close a given AVCodecContext and free all the data associated with it (but not the AVCodecContext itself)
diff --git a/src/AvTranscoder/properties/VideoProperties.hpp b/src/AvTranscoder/properties/VideoProperties.hpp
@@ -47,13 +47,6 @@ class AvExport VideoProperties : public StreamProperties
     size_t getTicksPerFrame() const;
     size_t getWidth() const;
     size_t getHeight() const;
-
-    /**
-     * @return the distance between two nearest I frame
-     * @note it returns 0 for intra_only
-     */
-    size_t getGopSize() const;
-
     size_t getDtgActiveFormat() const;
     size_t getReferencesFrames() const;
     int getProfile() const;
@@ -77,6 +70,10 @@ class AvExport VideoProperties : public StreamProperties
     // @see analyseGopStructure
     bool isInterlaced() const { return _isInterlaced; }
     bool isTopFieldFirst() const { return _isTopFieldFirst; }
+    /**
+     * @return the distance between two nearest I frame
+     */
+    size_t getGopSize() const { return _gopSize; }
     std::vector<std::pair<char, bool> > getGopStructure() const { return _gopStructure; }
 //@}
 
@@ -120,6 +117,7 @@ class AvExport VideoProperties : public StreamProperties
     // Can acces these data when analyse first gop
     bool _isInterlaced;
     bool _isTopFieldFirst;
+    size_t _gopSize;
     std::vector<std::pair<char, bool> > _gopStructure;
     //@}
 
