[mythtv-users] Problem with MPEG-4 transcoded file (no bitrate or duration)

[John Pilkington]

On 13/05/2019 05:12, mythtv at kosowsky.org wrote:
> mythtv at kosowsky.org wrote at about 00:00:23 -0400 on Monday, May 13, 2019:
>   > In my old mythtv box (v24), I had no problem transcoding recordings to
>   > MPEG4 and then editing (i.e. cutting) the video in the mythtv editor.
>   >
>   > For example, a transcoded and edited file, shows up under ffmpeg -i
>   > as:
>   >     Duration: 00:19:16.47, start: 0.033000, bitrate: 1411 kb/s
>   >         Stream #0:0: Video: mpeg4 (Simple Profile) (DIVX / 0x58564944), yuv420p, 720x480 [SAR 1:1 DAR 3:2], SAR 32:27 DAR 16:9, 29.97 fps, 29.97 tbr, 1k tbn, 30k tbc
>   >         Stream #0:1: Audio: mp3 (LAME / 0x454D414C), 48000 Hz, stereo, s16p, 1411 kb/s
>   > 	
>   > Under v29.1, when I transcode to mpeg4, the file seems to transcode (and compress) properly and I have no problem playing it.
>   > But, when I try to edit it, the timestamps are all wrong, so that when I use the editor to cut and re-transcode, the cut list is not properly applied and the file is not spliced together properly.
>   > When I run 'ffmpeg -i' I see that both the "Duration" and the "bitrate" are 'N/A', presumably explaining why the timestamps are wrong.
>   >     Duration: N/A, start: 60704.885000, bitrate: N/A
>   >         Stream #0:0: Video: mpeg4 (Simple Profile) (DIVX / 0x58564944), yuv420p, 704x480 [SAR 1:1 DAR 22:15], SAR 40:33 DAR 16:9, 29.97 fps, 29.97 tbr, 1k tbn, 30k tbc
>   >         Stream #0:1: Audio: mp3 (LAME / 0x454D414C), 48000 Hz, stereo, s16p, 1411 kb/s
>   >
>   > I tried using 'mythcommflag --rebuild --file' to rebuild the seektable (which has saved me other times), but id had no effect.
>   >
>   > Is there something broken with mythtranscode that causes the file to create transcodings without defined durations or timestamps?
>   >
>   > Again, I never had the problem in (much) older version of mythtv...
>   >
>   > Thanks,
>   > Jeff
> 
> Note the transcoding profile I use is as follows:
> 	Autodetect from MPEG2
> 	    Profile name: MPEG2
> 	    Enable auto-transcode after recording: yes
> 	    Width: 720
> 	    Height: 480
> 	    Video Compression: MPEG-4
> 	    Bitrate (kb/s): 3300
> 	    Maximum quality: 2
> 	    Minimum quality: 15
> 	    Max quality difference between frames: 3
> 	    Scale bitrate for frame size: No
> 	    Enable high-quality recording: Yes
> 	    Enable 4MV encoding: Yes
> 	    Enable interlaced DCT encoding: No
> 	    Enable interlaced motion estimation: No
> 	    Number of threads: 4
> 			
> 	    Audio Quality: MP3

I have never used mythtranscode with a format like that, but it seems 
likely that your problem is actually an incompatibility with 
mythcommflag --rebuild, or its equivalent within mythtranscode.

It's not clear to me why you can't do the editing before transcoding, 
either directly to MPEG-4 or using mythtranscode --mpeg2 first.

John P