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rsv-ben: fix fps detection for CFR reference clips #286

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rsv-ben: fix fps detection for CFR reference clips #286

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16 changes: 14 additions & 2 deletions src/rsv.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,14 @@ void Mp4::repairRsvBen(const string& filename) {
if (video_track_idx >= 0) {
Track& video_track = tracks_[video_track_idx];
video_timescale = video_track.timescale_;
if (!video_track.times_.empty()) {
// CFR reference clips (all Sony cameras) collapse stts into
// constant_duration_ and leave times_ empty. Must read it, otherwise
// video_duration_per_sample keeps its 1000 default -> fps wrongly 24
// instead of 23.976 (24000/1001) -> audio chunk size off by ~96
// bytes/GOP -> 1 corrupt video frame/GOP + short audio.
if (video_track.constant_duration_ != -1) {
video_duration_per_sample = video_track.constant_duration_;
} else if (!video_track.times_.empty()) {
video_duration_per_sample = video_track.times_[0];
}
logg(V, "video timescale: ", video_timescale, ", duration per sample: ", video_duration_per_sample, "\n");
Expand Down Expand Up @@ -216,7 +223,12 @@ void Mp4::repairRsvBen(const string& filename) {
// Audio samples per chunk = GOP duration * audio_sample_rate
double fps = (double)video_timescale / video_duration_per_sample;
double gop_duration_sec = (double)frames_per_gop / fps;
int audio_samples_per_chunk = (int)(gop_duration_sec * audio_sample_rate);
// Exact integer rational: samples = frames_per_gop * sample_rate *
// dur_per_sample / timescale (rounded). Avoids float truncation that
// would drop a sample and re-introduce the boundary error.
int audio_samples_per_chunk = (int)(
((long long)frames_per_gop * audio_sample_rate * video_duration_per_sample
+ video_timescale / 2) / video_timescale);
int audio_chunk_size_per_track = audio_samples_per_chunk * audio_sample_size;
// Total audio size in RSV is for all tracks combined
int total_audio_chunk_size = audio_chunk_size_per_track * max(1, num_audio_tracks);
Expand Down