Better support for audio only webm files.

Changed max_cluster_duration to 30 seconds so default command line
will not crash on audio only WebM files. Added support to the sample
muxer to output cues on the audio track. Created a muxer helper
function to clean up the code a little.

Change-Id: I2871836b64cef7defd10aa51a209b4abd9046832

mkvmuxer.cpp

@@ -1128,7 +1128,7 @@ Segment::Segment(IMkvWriter* writer)
       has_video_(false),
       header_written_(false),
       last_timestamp_(0),
-      max_cluster_duration_(0),
+      max_cluster_duration_(30000000000),
       max_cluster_size_(0),
       mode_(kFile),
       new_cluster_(true),
@@ -1252,34 +1252,8 @@ bool Segment::AddFrame(uint8* frame,
                        bool is_key) {
   assert(frame);
 
-  if (!header_written_) {
-    if (!WriteSegmentHeader())
-      return false;
-
-    if (!seek_head_.AddSeekEntry(kMkvCluster,
-                                 writer_->Position() - payload_pos_))
-      return false;
-
-    if (output_cues_ && cues_track_ == 0) {
-      // Check for a video track
-      for (uint32 i = 0; i < tracks_.track_entries_size(); ++i) {
-        const Track* const track = tracks_.GetTrackByIndex(i);
-        assert(track);
-
-        if (tracks_.TrackIsVideo(track->number())) {
-          cues_track_ = track->number();
-          break;
-        }
-      }
-
-      // Set first track found
-      if (cues_track_ == 0) {
-        const Track* const track = tracks_.GetTrackByIndex(0);
-        assert(track);
-        cues_track_ = track->number();
-      }
-    }
-  }
+  if (!CheckHeaderInfo())
+    return false;
 
   // If the segment has a video track hold onto audio frames to make sure the
   // audio that is associated with the start time of a video key-frame is
@@ -1472,6 +1446,38 @@ bool Segment::WriteSegmentHeader() {
   return true;
 }
 
+bool Segment::CheckHeaderInfo() {
+  if (!header_written_) {
+    if (!WriteSegmentHeader())
+      return false;
+
+    if (!seek_head_.AddSeekEntry(kMkvCluster,
+                                 writer_->Position() - payload_pos_))
+      return false;
+
+    if (output_cues_ && cues_track_ == 0) {
+      // Check for a video track
+      for (uint32 i = 0; i < tracks_.track_entries_size(); ++i) {
+        const Track* const track = tracks_.GetTrackByIndex(i);
+        assert(track);
+
+        if (tracks_.TrackIsVideo(track->number())) {
+          cues_track_ = track->number();
+          break;
+        }
+      }
+
+      // Set first track found
+      if (cues_track_ == 0) {
+        const Track* const track = tracks_.GetTrackByIndex(0);
+        assert(track);
+        cues_track_ = track->number();
+      }
+    }
+  }
+  return true;
+}
+
 bool Segment::AddCuePoint(uint64 timestamp) {
   assert(cluster_list_size_ > 0);
   const Cluster* const cluster = cluster_list_[cluster_list_size_-1];

mkvmuxer.hpp

@@ -592,6 +592,11 @@ class Segment {
   // nanoseconds of the cue's time. Returns true on success.
   bool AddCuePoint(uint64 timestamp);
 
+  // Checks if header information has been output and initialized. If not it
+  // will output the Segment element and initialize the SeekHead elment and
+  // Cues elements.
+  bool CheckHeaderInfo();
+
   // Adds the frame to our frame array.
   bool QueueFrame(Frame* frame);
 
@@ -648,8 +653,8 @@ class Segment {
   uint64 last_timestamp_;
 
   // Maximum time in nanoseconds for a cluster duration. This variable is a
-  // guideline and some clusters may have a longer duration. Default is 0
-  // which signifies that the muxer will decide.
+  // guideline and some clusters may have a longer duration. Default is 30
+  // seconds.
   uint64 max_cluster_duration_;
 
   // Maximum size in bytes for a cluster. This variable is a guideline and

sample_muxer/sample_muxer.cpp

@@ -31,6 +31,7 @@ void Usage() {
   printf("                              0 puts the muxer into file mode\n");
   printf("  -output_cues <int>          >0 outputs cues element\n");
   printf("  -cues_on_video_track <int>  >0 outputs cues on video track\n");
+  printf("  -cues_on_audio_track <int>  >0 outputs cues on audio track\n");
   printf("                              0 outputs cues on audio track\n");
   printf("  -max_cluster_duration <double> in seconds\n");
   printf("  -max_cluster_size <int>     in bytes\n");
@@ -59,6 +60,7 @@ int main(int argc, char* argv[]) {
   bool live_mode = false;
   bool output_cues = true;
   bool cues_on_video_track = true;
+  bool cues_on_audio_track = true;
   uint64 max_cluster_duration = 0;
   uint64 max_cluster_size = 0;
   bool switch_tracks = false;
@@ -89,6 +91,8 @@ int main(int argc, char* argv[]) {
       output_cues = strtol(argv[++i], &end, 10) == 0 ? false : true;
     } else if (!strcmp("-cues_on_video_track", argv[i])) {
       cues_on_video_track = strtol(argv[++i], &end, 10) == 0 ? false : true;
+    } else if (!strcmp("-cues_on_audio_track", argv[i])) {
+      cues_on_audio_track = strtol(argv[++i], &end, 10) == 0 ? false : true;
     } else if (!strcmp("-max_cluster_duration", argv[i])) {
       const double seconds = strtod(argv[++i], &end);
       max_cluster_duration =
@@ -278,7 +282,8 @@ int main(int argc, char* argv[]) {
   if (cues_on_video_track) {
     if (vid_track)
       muxer_segment.CuesTrack(vid_track);
-  } else {
+  }
+  if (cues_on_audio_track) {
     if (aud_track)
       muxer_segment.CuesTrack(aud_track);
   }