fftools/ffmpeg_mux_init: default to input timebase for streamcopy

Stop trying to invent some "framerate-based" timebase when there is no
reason to think the stream is CFR at all.

fftools/ffmpeg_mux_init.c

@@ -960,17 +960,12 @@ static int streamcopy_init(const Muxer *mux, OutputStream *ost, AVDictionary **e
     else
         ost->st->avg_frame_rate = ist->st->avg_frame_rate;
 
-    ret = avformat_transfer_internal_stream_timing_info(mux->fc->oformat,
-                                                        ost->st, ist->st, copy_tb);
-    if (ret < 0)
-        goto fail;
-
     // copy timebase while removing common factors
     if (ost->st->time_base.num <= 0 || ost->st->time_base.den <= 0) {
         if (fr.num)
             ost->st->time_base = av_inv_q(fr);
         else
-            ost->st->time_base = av_add_q(av_stream_get_codec_timebase(ost->st), (AVRational){0, 1});
+            ost->st->time_base = av_add_q(ist->st->time_base, (AVRational){0, 1});
     }
 
     if (!ms->copy_prior_start) {

tests/fate/ffmpeg.mak

@@ -146,7 +146,7 @@ fate-copy-trac236: CMD = transcode mov $(TARGET_SAMPLES)/mov/fcp_export8-236.mov
 
 FATE_STREAMCOPY-$(call TRANSCODE, RAWVIDEO MPEG2VIDEO, MXF, MPEGTS_DEMUXER MPEGVIDEO_PARSER MPEGAUDIO_PARSER MP2_DECODER ARESAMPLE_FILTER PCM_S16LE_DECODER) += fate-copy-trac4914
 fate-copy-trac4914: CMD = transcode mpegts $(TARGET_SAMPLES)/mpeg2/xdcam8mp2-1s_small.ts\
-                      mxf "-c:a pcm_s16le -af aresample -c:v copy"
+                      mxf "-c:a pcm_s16le -af aresample -c:v copy -time_base 1001/30000"
 
 FATE_STREAMCOPY-$(call TRANSCODE, RAWVIDEO MPEG2VIDEO, AVI, MPEGTS_DEMUXER MPEGVIDEO_PARSER MPEGAUDIO_PARSER EXTRACT_EXTRADATA_BSF MP2_DECODER ARESAMPLE_FILTER) += fate-copy-trac4914-avi
 fate-copy-trac4914-avi: CMD = transcode mpegts $(TARGET_SAMPLES)/mpeg2/xdcam8mp2-1s_small.ts\

tests/ref/fate/copy-trac4914-avi

@@ -1,5 +1,5 @@
-26e4202638bc384b82d2b5eb4d33a5f0 *tests/data/fate/copy-trac4914-avi.avi
-479494 tests/data/fate/copy-trac4914-avi.avi
+3b6f31b806ef421652a066f239536b0d *tests/data/fate/copy-trac4914-avi.avi
+492046 tests/data/fate/copy-trac4914-avi.avi
 #tb 0: 1001/30000
 #media_type 0: video
 #codec_id 0: rawvideo