From 2704fe5ce4ecfcb9214c032117be719079b93d89 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Thu, 28 Jul 2016 00:44:40 +0100
Subject: [PATCH] Fix start-trim of audio-only content (#915).

---
 ChangeLog                 |  4 ++++
 src/lib/ffmpeg_decoder.cc | 18 ++++++++++++++++--
 src/lib/ffmpeg_stream.cc  | 15 +++++++++++++++
 src/lib/ffmpeg_stream.h   |  6 ++++++
 4 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index a099425f6..8904eef6c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2016-07-28  Carl Hetherington  <cth@carlh.net>
+
+	* Fix start-trim of audio-only content (#915).
+
 2016-07-26  Carl Hetherington  <cth@carlh.net>
 
 	* Expand vertical size of servers list in preferences (#913).
diff --git a/src/lib/ffmpeg_decoder.cc b/src/lib/ffmpeg_decoder.cc
index 164785c83..f7c435a74 100644
--- a/src/lib/ffmpeg_decoder.cc
+++ b/src/lib/ffmpeg_decoder.cc
@@ -40,6 +40,7 @@
 #include "audio_decoder.h"
 #include "compose.hpp"
 #include "subtitle_content.h"
+#include "audio_content.h"
 #include <dcp/subtitle_string.h>
 #include <sub/ssa_reader.h>
 #include <sub/subtitle.h>
@@ -73,6 +74,8 @@ using std::map;
 using boost::shared_ptr;
 using boost::is_any_of;
 using boost::split;
+using boost::optional;
+using boost::dynamic_pointer_cast;
 using dcp::Size;
 
 FFmpegDecoder::FFmpegDecoder (shared_ptr<const FFmpegContent> c, shared_ptr<Log> log)
@@ -326,7 +329,18 @@ FFmpegDecoder::seek (ContentTime time, bool accurate)
 	   http://www.mjbshaw.com/2012/04/seeking-in-ffmpeg-know-your-timestamp.html
 	*/
 
-	DCPOMATIC_ASSERT (_video_stream);
+	optional<int> stream;
+
+	if (_video_stream) {
+		stream = _video_stream;
+	} else {
+		shared_ptr<FFmpegAudioStream> s = dynamic_pointer_cast<FFmpegAudioStream> (_ffmpeg_content->audio->stream ());
+		if (s) {
+			stream = s->index (_format_context);
+		}
+	}
+
+	DCPOMATIC_ASSERT (stream);
 
 	ContentTime u = time - _pts_offset;
 	if (u < ContentTime ()) {
@@ -376,7 +390,7 @@ FFmpegDecoder::decode_audio_packet ()
 		if (decode_result < 0) {
 			/* avcodec_decode_audio4 can sometimes return an error even though it has decoded
 			   some valid data; for example dca_subframe_footer can return AVERROR_INVALIDDATA
-			   if it overreads the auxiliary data.  ffplay carries on if frame_finished is true,
+			   if it overreads the auxiliary data.	ffplay carries on if frame_finished is true,
 			   even in the face of such an error, so I think we should too.
 
 			   Returning from the method here caused mantis #352.
diff --git a/src/lib/ffmpeg_stream.cc b/src/lib/ffmpeg_stream.cc
index 085c78fa8..7a8748e4e 100644
--- a/src/lib/ffmpeg_stream.cc
+++ b/src/lib/ffmpeg_stream.cc
@@ -62,3 +62,18 @@ FFmpegStream::stream (AVFormatContext const * fc) const
 	DCPOMATIC_ASSERT (false);
 	return 0;
 }
+
+int
+FFmpegStream::index (AVFormatContext const * fc) const
+{
+	size_t i = 0;
+	while (i < fc->nb_streams) {
+		if (fc->streams[i]->id == _id) {
+			return i;
+		}
+		++i;
+	}
+
+	DCPOMATIC_ASSERT (false);
+	return 0;
+}
diff --git a/src/lib/ffmpeg_stream.h b/src/lib/ffmpeg_stream.h
index 317ee2e9c..ec27a30f0 100644
--- a/src/lib/ffmpeg_stream.h
+++ b/src/lib/ffmpeg_stream.h
@@ -54,6 +54,12 @@ public:
 		return boost::lexical_cast<std::string> (_id);
 	}
 
+	int id () const {
+		return _id;
+	}
+
+	int index (AVFormatContext const * c) const;
+
 	std::string name;
 
 	friend bool operator== (FFmpegStream const & a, FFmpegStream const & b);
-- 
2.30.2