Detect soft 2:3 pulldown (telecine) files and decode them at 23.976.

[dcpomatic.git] / src / lib / ffmpeg_examiner.cc

diff --git a/src/lib/ffmpeg_examiner.cc b/src/lib/ffmpeg_examiner.cc
index b31280cd5b3cac7b093456e2c9cb2c946a71635a..1a2c49f1cdfd66dcfd77e63f312255cbf4533be8 100644 (file)
--- a/src/lib/ffmpeg_examiner.cc
+++ b/src/lib/ffmpeg_examiner.cc
@@ -18,6 +18,7 @@
 
 */
 
+#include "dcpomatic_log.h"
 extern "C" {
 #include <libavcodec/avcodec.h>
 #include <libavformat/avformat.h>
@@ -40,14 +41,22 @@ extern "C" {
 using std::string;
 using std::cout;
 using std::max;
+using std::vector;
 using boost::shared_ptr;
 using boost::optional;
 
+/* This is how many frames from the start of any video that we will examine to see if we
+ * can spot soft 2:3 pull-down ("telecine").
+ */
+static const int PULLDOWN_CHECK_FRAMES = 16;
+
+
 /** @param job job that the examiner is operating in, or 0 */
 FFmpegExaminer::FFmpegExaminer (shared_ptr<const FFmpegContent> c, shared_ptr<Job> job)
        : FFmpeg (c)
        , _video_length (0)
        , _need_video_length (false)
+       , _pulldown (false)
 {
        /* Find audio and subtitle streams */
 
@@ -100,9 +109,15 @@ FFmpegExaminer::FFmpegExaminer (shared_ptr<const FFmpegContent> c, shared_ptr<Jo
        /* Run through until we find:
         *   - the first video.
         *   - the first audio for each stream.
+        *   - the top-field-first and repeat-first-frame values ("temporal_reference") for the first PULLDOWN_CHECK_FRAMES video frames.
         */
 
        int64_t const len = _file_group.length ();
+       /* A string which we build up to describe the top-field-first and repeat-first-frame values for the first few frames.
+        * It would be nicer to use something like vector<bool> here but we want to search the array for a pattern later,
+        * and a string seems a reasonably neat way to do that.
+        */
+       string temporal_reference;
        while (true) {
                int r = av_read_frame (_format_context, &_packet);
                if (r < 0) {
@@ -120,7 +135,7 @@ FFmpegExaminer::FFmpegExaminer (shared_ptr<const FFmpegContent> c, shared_ptr<Jo
                AVCodecContext* context = _format_context->streams[_packet.stream_index]->codec;
 
                if (_video_stream && _packet.stream_index == _video_stream.get()) {
-                       video_packet (context);
+                       video_packet (context, temporal_reference);
                }
 
                bool got_all_audio = true;
@@ -136,7 +151,7 @@ FFmpegExaminer::FFmpegExaminer (shared_ptr<const FFmpegContent> c, shared_ptr<Jo
 
                av_packet_unref (&_packet);
 
-               if (_first_video && got_all_audio) {
+               if (_first_video && got_all_audio && temporal_reference.size() >= PULLDOWN_CHECK_FRAMES) {
                        /* All done */
                        break;
                }
@@ -165,14 +180,33 @@ FFmpegExaminer::FFmpegExaminer (shared_ptr<const FFmpegContent> c, shared_ptr<Jo
 
                DCPOMATIC_ASSERT (fabs (*_rotation - 90 * round (*_rotation / 90)) < 2);
        }
+
+       LOG_GENERAL("Temporal reference was %1", temporal_reference);
+       if (temporal_reference.find("T2T3B2B3T2T3B2B3") || temporal_reference.find("B2B3T2T3B2B3T2T3")) {
+               /* The magical sequence (taken from mediainfo) suggests that 2:3 pull-down is in use */
+               _pulldown = true;
+               LOG_GENERAL_NC("Suggest that this may be 2:3 pull-down (soft telecine)");
+       }
+
+#ifdef DCPOMATIC_VARIANT_SWAROOP
+       AVDictionaryEntry* e = av_dict_get (_format_context->metadata, SWAROOP_ID_TAG, 0, 0);
+       if (e) {
+               _id = e->value;
+       }
+#endif
 }
 
+
+/** @param temporal_reference A string to which we should add two characters per frame;
+ *  the first   is T or B depending on whether it's top- or bottom-field first,
+ *  ths seconds is 3 or 2 depending on whether "repeat_pict" is true or not.
+ */
 void
-FFmpegExaminer::video_packet (AVCodecContext* context)
+FFmpegExaminer::video_packet (AVCodecContext* context, string& temporal_reference)
 {
        DCPOMATIC_ASSERT (_video_stream);
 
-       if (_first_video && !_need_video_length) {
+       if (_first_video && !_need_video_length && temporal_reference.size() >= PULLDOWN_CHECK_FRAMES) {
                return;
        }
 
@@ -186,6 +220,10 @@ FFmpegExaminer::video_packet (AVCodecContext* context)
                                _format_context->streams[_video_stream.get()]
                                ).get_value_or (ContentTime ()).frames_round (video_frame_rate().get ());
                }
+               if (temporal_reference.size() < PULLDOWN_CHECK_FRAMES) {
+                       temporal_reference += (_frame->top_field_first ? "T" : "B");
+                       temporal_reference += (_frame->repeat_pict ? "3" : "2");
+               }
        }
 }