LibMedia: Separate file duration from track duration in Demuxer

Most users will only care about the total file duration, and shouldn't
be required to determine the file duration from multiple track
durations. To facilitate that, add a total_duration() function that
returns the demuxer's duration not associated to any particular track.

Libraries/LibMedia/Containers/Matroska/MatroskaDemuxer.cpp

@@ -4,7 +4,9 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/Assertions.h>
 #include <AK/Debug.h>
+#include <LibMedia/DecoderError.h>
 
 #include "MatroskaDemuxer.h"
 
@@ -192,10 +194,15 @@ DecoderErrorOr<Sample> MatroskaDemuxer::get_next_sample_for_track(Track track)
     return Sample(status.block->timestamp(), move(sample_data), VideoSampleData(cicp));
 }
 
-DecoderErrorOr<AK::Duration> MatroskaDemuxer::duration(Track)
+DecoderErrorOr<AK::Duration> MatroskaDemuxer::total_duration()
 {
     auto duration = TRY(m_reader.segment_information()).duration();
     return duration.value_or(AK::Duration::zero());
 }
 
+DecoderErrorOr<AK::Duration> MatroskaDemuxer::duration_of_track(Track const&)
+{
+    return total_duration();
+}
+
 }

Libraries/LibMedia/Containers/Matroska/MatroskaDemuxer.h

@@ -32,7 +32,8 @@ public:
 
     DecoderErrorOr<Optional<AK::Duration>> seek_to_most_recent_keyframe(Track track, AK::Duration timestamp, Optional<AK::Duration> earliest_available_sample = OptionalNone()) override;
 
-    DecoderErrorOr<AK::Duration> duration(Track track) override;
+    DecoderErrorOr<AK::Duration> duration_of_track(Track const& track) override;
+    DecoderErrorOr<AK::Duration> total_duration() override;
 
     DecoderErrorOr<CodecID> get_codec_id_for_track(Track track) override;
 

Libraries/LibMedia/Demuxer.h

@@ -36,7 +36,8 @@ public:
     // in the case that the timestamp is closer to the current time than the nearest keyframe.
     virtual DecoderErrorOr<Optional<AK::Duration>> seek_to_most_recent_keyframe(Track track, AK::Duration timestamp, Optional<AK::Duration> earliest_available_sample = OptionalNone()) = 0;
 
-    virtual DecoderErrorOr<AK::Duration> duration(Track track) = 0;
+    virtual DecoderErrorOr<AK::Duration> duration_of_track(Track const&) = 0;
+    virtual DecoderErrorOr<AK::Duration> total_duration() = 0;
 };
 
 }

Libraries/LibMedia/FFmpeg/FFmpegDemuxer.cpp

@@ -68,6 +68,15 @@ static inline AK::Duration time_units_to_duration(i64 time_units, AVRational con
     return time_units_to_duration(time_units, time_base.num, time_base.den);
 }
 
+DecoderErrorOr<AK::Duration> FFmpegDemuxer::total_duration()
+{
+    if (m_format_context->duration < 0) {
+        return DecoderError::format(DecoderErrorCategory::Unknown, "Negative stream duration");
+    }
+
+    return time_units_to_duration(m_format_context->duration, 1, AV_TIME_BASE);
+}
+
 DecoderErrorOr<AK::Duration> FFmpegDemuxer::duration_of_track(Track const& track)
 {
     VERIFY(track.identifier() < m_format_context->nb_streams);
@@ -78,11 +87,7 @@ DecoderErrorOr<AK::Duration> FFmpegDemuxer::duration_of_track(Track const& track
     }
 
     // If the stream doesn't specify the duration, fallback to what the container says the duration is.
-    // If the container doesn't know the duration, then we're out of luck. Return an error.
-    if (m_format_context->duration < 0)
-        return DecoderError::format(DecoderErrorCategory::Unknown, "Negative stream duration");
-
-    return time_units_to_duration(m_format_context->duration, 1, AV_TIME_BASE);
+    return total_duration();
 }
 
 DecoderErrorOr<Track> FFmpegDemuxer::get_track_for_stream_index(u32 stream_index)
@@ -144,11 +149,6 @@ DecoderErrorOr<Optional<AK::Duration>> FFmpegDemuxer::seek_to_most_recent_keyfra
     return timestamp;
 }
 
-DecoderErrorOr<AK::Duration> FFmpegDemuxer::duration(Track track)
-{
-    return duration_of_track(track);
-}
-
 DecoderErrorOr<CodecID> FFmpegDemuxer::get_codec_id_for_track(Track track)
 {
     VERIFY(track.identifier() < m_format_context->nb_streams);

Libraries/LibMedia/FFmpeg/FFmpegDemuxer.h

@@ -30,7 +30,8 @@ public:
 
     virtual DecoderErrorOr<Optional<AK::Duration>> seek_to_most_recent_keyframe(Track track, AK::Duration timestamp, Optional<AK::Duration> earliest_available_sample = OptionalNone()) override;
 
-    virtual DecoderErrorOr<AK::Duration> duration(Track track) override;
+    virtual DecoderErrorOr<AK::Duration> duration_of_track(Track const&) override;
+    virtual DecoderErrorOr<AK::Duration> total_duration() override;
 
     virtual DecoderErrorOr<CodecID> get_codec_id_for_track(Track track) override;
 
@@ -39,7 +40,6 @@ public:
     virtual DecoderErrorOr<Sample> get_next_sample_for_track(Track track) override;
 
 private:
-    DecoderErrorOr<AK::Duration> duration_of_track(Track const& track);
     DecoderErrorOr<Track> get_track_for_stream_index(u32 stream_index);
 
     NonnullOwnPtr<SeekableStream> m_stream;

Libraries/LibMedia/PlaybackManager.cpp

@@ -90,7 +90,7 @@ AK::Duration PlaybackManager::duration()
 {
     auto duration_result = ({
         auto demuxer_locker = Threading::MutexLocker(m_decoder_mutex);
-        m_demuxer->duration(m_selected_video_track);
+        m_demuxer->duration_of_track(m_selected_video_track);
     });
     if (duration_result.is_error()) {
         dispatch_decoder_error(duration_result.release_error());