demux: make ALBUM ReplayGain tags optional when using libavformat

Commit e392d6610d1e35cc0190c794c151211b0aae83e6 modified the native
demuxer to use track gain as a fallback for album gain if the latter is
not present. This commit makes functionally equivalent changes in the
libavformat demuxer.

1 files changed, 5 insertions, 0 deletions

diff --git a/demux/demux.c b/demux/demux.c
index f02f9b77aa..a8b392d74e 100644
--- a/demux/demux.c
+++ b/demux/demux.c
@@ -1946,12 +1946,17 @@ static struct replaygain_data *decode_rgain(struct mp_log *log,
 {
     struct replaygain_data rg = {0};
 
+    // Set values in *rg, using track gain as a fallback for album gain if the
+    // latter is not present. This behavior matches that in demux/demux_lavf.c's
+    // export_replaygain; if you change this, please make equivalent changes
+    // there too.
     if (decode_gain(log, tags, "REPLAYGAIN_TRACK_GAIN", &rg.track_gain) >= 0 &&
         decode_peak(log, tags, "REPLAYGAIN_TRACK_PEAK", &rg.track_peak) >= 0)
     {
         if (decode_gain(log, tags, "REPLAYGAIN_ALBUM_GAIN", &rg.album_gain) < 0 ||
             decode_peak(log, tags, "REPLAYGAIN_ALBUM_PEAK", &rg.album_peak) < 0)
         {
+            // Album gain is undefined; fall back to track gain.
             rg.album_gain = rg.track_gain;
             rg.album_peak = rg.track_peak;
         }