In this ffmpeg output listing: Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, top first), 720x480 [SAR 32:27 DAR 16:9], Closed Captions, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc what does "tbr", "tbn", and "tbc" mean? I've searched the documentation but have not found Joy. Thanks!