movenc: use similar logic to DASH when writing bit rate to ISML

This way, in case of bit rate not being set, max_rate will be used
instead. This enables, for example, remuxing of MPEG-TS to ISMV+ISML
without losing general bit rate information.

libavformat/movenc.c

@@ -3581,6 +3581,8 @@ static int mov_write_isml_manifest(AVIOContext *pb, MOVMuxContext *mov, AVFormat
 {
     int64_t pos = avio_tell(pb);
     int i;
+    int64_t manifest_bit_rate = 0;
+
     static const uint8_t uuid[] = {
         0xa5, 0xd4, 0x0b, 0x30, 0xe8, 0x14, 0x11, 0xdd,
         0xba, 0x2f, 0x08, 0x00, 0x20, 0x0c, 0x9a, 0x66
@@ -3615,9 +3617,13 @@ static int mov_write_isml_manifest(AVIOContext *pb, MOVMuxContext *mov, AVFormat
         } else {
             continue;
         }
+
+        AVCPBProperties *props = (AVCPBProperties*)av_stream_get_side_data(track->st, AV_PKT_DATA_CPB_PROPERTIES, NULL);
+
+        manifest_bit_rate = track->par->bit_rate ? track->par->bit_rate : props ? props->max_bitrate : 0;
         avio_printf(pb, "<%s systemBitrate=\"%"PRId64"\">\n", type,
-                    (int64_t)track->par->bit_rate);
-        param_write_int(pb, "systemBitrate", track->par->bit_rate);
+                    (int64_t)manifest_bit_rate);
+        param_write_int(pb, "systemBitrate", manifest_bit_rate);
         param_write_int(pb, "trackID", track_id);
         if (track->par->codec_type == AVMEDIA_TYPE_VIDEO) {
             if (track->par->codec_id == AV_CODEC_ID_H264) {