obs-outputs: File splitting improvements for Hybrid MP4/MOV

plugins/obs-outputs/mp4-mux.c

@@ -2501,18 +2501,30 @@ static void process_packets(struct mp4_mux *mux, struct mp4_track *track, uint64
 	if (!count)
 		return;
 
-	/* Only iterate upt to penultimate packet so we can determine duration
-	 * for all processed packets. */
-	for (size_t i = 0; i < count - 1; i++) {
+	/* Unless it is the final flush, only iterate up to penultimate packet so we can determine duration for all
+	 * processed packets. */
+	const bool final_flush = mux->next_frag_pts == 0;
+	const size_t end_offset = final_flush ? 0 : 1;
+
+	for (size_t i = 0; i < count - end_offset; i++) {
 		struct encoder_packet *pkt = get_pkt_at(&track->packets, i);
 
-		if (mux->next_frag_pts && packet_pts_usec(pkt) >= mux->next_frag_pts)
+		if (!final_flush && packet_pts_usec(pkt) >= mux->next_frag_pts)
 			break;
 
-		struct encoder_packet *next = get_pkt_at(&track->packets, i + 1);
+		uint32_t duration;
+		if (i < count - 1) {
+			/* If a next packet is available: Duration is just distance between current and next DTS. */
+			struct encoder_packet *next = get_pkt_at(&track->packets, i + 1);
+			duration = (uint32_t)(next->dts - pkt->dts);
+		} else {
+			/* If this is the last packet, and we're doing a final flush: Reuse the previous duration */
+			if (!track->fragment_samples.num)
+				break; /* no previous sample */
+
+			duration = track->fragment_samples.array[track->fragment_samples.num - 1].duration;
+		}
 
-		/* Duration is just distance between current and next DTS. */
-		uint32_t duration = (uint32_t)(next->dts - pkt->dts);
 		uint32_t sample_count = 1;
 		uint32_t size = (uint32_t)pkt->size;
 		int32_t offset = (int32_t)(pkt->pts - pkt->dts);

plugins/obs-outputs/mp4-output.c

@@ -51,6 +51,7 @@ struct mp4_output {
 	struct serializer serializer;
 
 	bool enable_bpm;
+	bool received_first_keyframe;
 
 	volatile bool active;
 	volatile bool stopping;
@@ -348,8 +349,11 @@ static inline bool should_split(struct mp4_output *out, struct encoder_packet *p
 		return true;
 
 	/* reached maximum duration */
-	if (out->max_time > 0 && packet->dts_usec - out->start_time >= out->max_time)
-		return true;
+	if (out->max_time > 0) {
+		const int64_t current_runtime = packet->dts_usec - out->start_time;
+		/* Allow a small error in timestamps (up to 1 ms). */
+		return llabs(out->max_time - current_runtime) < 1000LL;
+	}
 
 	return false;
 }
@@ -532,6 +536,13 @@ static void mp4_output_packet(void *data, struct encoder_packet *packet)
 		}
 	}
 
+	/* Correct start time for b-frames */
+	if (!out->received_first_keyframe && packet->type == OBS_ENCODER_VIDEO && packet->track_idx == 0 &&
+	    packet->keyframe) {
+		out->start_time = packet->dts_usec;
+		out->received_first_keyframe = true;
+	}
+
 	if (out->split_file_enabled) {
 		if (out->split_buffer.num) {
 			int64_t pts_usec = packet_pts_usec(packet);