VSE: Fix audaspace not reading ffmpeg files with start offset correctly

The duration and start time for audio strips were not correctly read in
audaspace.

Some video files have a "lead in" section of audio that plays before the
video starts playing back. Before this patch, we would play this lead in
audio at the same time as the video started and thus the audio would not
be in sync anymore.

Now the lead in audio is cut off and the duration should be correctly
calculated with this in mind.

If the audio starts after the video, the audio strip is shifted to
account for this, but it will also lead to cut off audio which might not
be wanted. However we don't have a simple way to solve this at this
point.

Differential Revision: http://developer.blender.org/D11917

1 files changed, 56 insertions, 24 deletions

diff --git a/extern/audaspace/plugins/ffmpeg/FFMPEGReader.cpp b/extern/audaspace/plugins/ffmpeg/FFMPEGReader.cpp
index b46f65eddbf..afdc7fcfcc6 100644
--- a/extern/audaspace/plugins/ffmpeg/FFMPEGReader.cpp
+++ b/extern/audaspace/plugins/ffmpeg/FFMPEGReader.cpp
@@ -68,7 +68,7 @@ int FFMPEGReader::decode(AVPacket& packet, Buffer& buffer)
 					for(int i = 0; i < m_frame->nb_samples; i++)
 					{
 						std::memcpy(((data_t*)buffer.getBuffer()) + buf_pos + ((m_codecCtx->channels * i) + channel) * single_size,
-							   m_frame->data[channel] + i * single_size, single_size);
+								 m_frame->data[channel] + i * single_size, single_size);
 					}
 				}
 			}
@@ -109,7 +109,7 @@ int FFMPEGReader::decode(AVPacket& packet, Buffer& buffer)
 				for(int i = 0; i < m_frame->nb_samples; i++)
 				{
 					std::memcpy(((data_t*)buffer.getBuffer()) + buf_pos + ((m_codecCtx->channels * i) + channel) * single_size,
-						   m_frame->data[channel] + i * single_size, single_size);
+							 m_frame->data[channel] + i * single_size, single_size);
 				}
 			}
 		}
@@ -126,7 +126,10 @@ int FFMPEGReader::decode(AVPacket& packet, Buffer& buffer)
 void FFMPEGReader::init()
 {
 	m_position = 0;
+	m_start_offset = 0.0f;
 	m_pkgbuf_left = 0;
+	m_st_time = 0;
+	m_duration = 0;
 
 	if(avformat_find_stream_info(m_formatCtx, nullptr) < 0)
 		AUD_THROW(FileException, "File couldn't be read, ffmpeg couldn't find the stream info.");
@@ -134,15 +137,41 @@ void FFMPEGReader::init()
 	// find audio stream and codec
 	m_stream = -1;
 
+	double dur_sec = 0;
+
 	for(unsigned int i = 0; i < m_formatCtx->nb_streams; i++)
 	{
 #ifdef FFMPEG_OLD_CODE
-		if((m_formatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO)
+		if(m_formatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO)
 #else
-		if((m_formatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO)
+		if(m_formatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO)
 #endif
-			&& (m_stream < 0))
 		{
+			AVStream *audio_stream = m_formatCtx->streams[i];
+			double audio_timebase = av_q2d(audio_stream->time_base);
+
+			if (audio_stream->start_time != AV_NOPTS_VALUE)
+			{
+				m_st_time = audio_stream->start_time;
+			}
+
+			int64_t ctx_start_time = 0;
+			if (m_formatCtx->start_time != AV_NOPTS_VALUE) {
+				ctx_start_time = m_formatCtx->start_time;
+			}
+
+			m_start_offset = m_st_time * audio_timebase - (double)ctx_start_time / AV_TIME_BASE;
+
+			if(audio_stream->duration != AV_NOPTS_VALUE)
+			{
+				dur_sec = audio_stream->duration * audio_timebase;
+			}
+			else
+			{
+				/* If the audio starts after the stream start time, subract this from the total duration. */
+				dur_sec = (double)m_formatCtx->duration / AV_TIME_BASE - m_start_offset;
+			}
+
 			m_stream=i;
 			break;
 		}
@@ -213,6 +242,7 @@ void FFMPEGReader::init()
 	}
 
 	m_specs.rate = (SampleRate) m_codecCtx->sample_rate;
+	m_duration = lround(dur_sec * m_codecCtx->sample_rate);
 }
 
 FFMPEGReader::FFMPEGReader(std::string filename) :
@@ -338,21 +368,17 @@ void FFMPEGReader::seek(int position)
 {
 	if(position >= 0)
 	{
-		uint64_t st_time = m_formatCtx->start_time;
-		uint64_t seek_pos = ((uint64_t)position) * ((uint64_t)AV_TIME_BASE) / ((uint64_t)m_specs.rate);
+		double pts_time_base =
+			av_q2d(m_formatCtx->streams[m_stream]->time_base);
 
-		if(st_time != AV_NOPTS_VALUE) {
-			seek_pos += st_time;
-		}
+		uint64_t seek_pts = (((uint64_t)position) / ((uint64_t)m_specs.rate)) / pts_time_base;
 
-		double pts_time_base = 
-			av_q2d(m_formatCtx->streams[m_stream]->time_base);
-		uint64_t pts_st_time =
-			((st_time != AV_NOPTS_VALUE) ? st_time : 0)
-			/ pts_time_base / (uint64_t) AV_TIME_BASE;
+		if(m_st_time != AV_NOPTS_VALUE) {
+			seek_pts += m_st_time;
+		}
 
 		// a value < 0 tells us that seeking failed
-		if(av_seek_frame(m_formatCtx, -1, seek_pos,
+		if(av_seek_frame(m_formatCtx, m_stream, seek_pts,
 				 AVSEEK_FLAG_BACKWARD | AVSEEK_FLAG_ANY) >= 0)
 		{
 			avcodec_flush_buffers(m_codecCtx);
@@ -374,7 +400,7 @@ void FFMPEGReader::seek(int position)
 					if(packet.pts != AV_NOPTS_VALUE)
 					{
 						// calculate real position, and read to frame!
-						m_position = (packet.pts - pts_st_time) * pts_time_base * m_specs.rate;
+						m_position = (packet.pts - m_st_time) * pts_time_base * m_specs.rate;
 
 						if(m_position < position)
 						{
@@ -405,8 +431,7 @@ void FFMPEGReader::seek(int position)
 int FFMPEGReader::getLength() const
 {
 	// return approximated remaning size
-	return (int)((m_formatCtx->duration * m_codecCtx->sample_rate)
-				 / AV_TIME_BASE)-m_position;
+	return m_duration - m_position;
 }
 
 int FFMPEGReader::getPosition() const
@@ -414,6 +439,11 @@ int FFMPEGReader::getPosition() const
 	return m_position;
 }
 
+double FFMPEGReader::getStartOffset() const
+{
+	return m_start_offset;
+}
+
 Specs FFMPEGReader::getSpecs() const
 {
 	return m_specs.specs;
@@ -450,11 +480,13 @@ void FFMPEGReader::read(int& length, bool& eos, sample_t* buffer)
 			// decode the package
 			pkgbuf_pos = decode(packet, m_pkgbuf);
 
-			// copy to output buffer
-			data_size = std::min(pkgbuf_pos, left * sample_size);
-			m_convert((data_t*) buf, (data_t*) m_pkgbuf.getBuffer(), data_size / AUD_FORMAT_SIZE(m_specs.format));
-			buf += data_size / AUD_FORMAT_SIZE(m_specs.format);
-			left -= data_size / sample_size;
+			if (packet.pts >= m_st_time) {
+				// copy to output buffer
+				data_size = std::min(pkgbuf_pos, left * sample_size);
+				m_convert((data_t*) buf, (data_t*) m_pkgbuf.getBuffer(), data_size / AUD_FORMAT_SIZE(m_specs.format));
+				buf += data_size / AUD_FORMAT_SIZE(m_specs.format);
+				left -= data_size / sample_size;
+			}
 		}
 		av_packet_unref(&packet);
 	}