[FFmpeg-user] Question about splitting video with dvd_nav_packet data streams

[David Favor]

Carl Eugen Hoyos wrote:
> David Favor <david <at> davidfavor.com> writes:
> 
>> My goal is to process every stream as follows...
>>
>> 1) adjust volume
>> 2) reduce bitrate
>> 3) retain all data streams (varies 1-3 data streams/VOB file)
> 
>> Probably the easiest way to handle this is just to split 
>> all the streams into separate files... process them... 
>> reassemble them...
> 
> As you have shown convincingly, this is not correct.
> Please try to apply all necessary changes in one 
> command, if it fails, please post the command line 
> together with the complete, uncut console output here.
> 
> Carl Eugen

So... for the command...

    ffmpeg -y -i VTS_01_0.VOB -c:a pcm_s16le -ar 44100 -ac 2 foo.wav -map 0:1 -c:v copy foo.vob -map 0:1 -c:d copy foo.data

    Input #0, mpeg, from 'VTS_01_0.VOB':
      Duration: 00:00:33.99, start: 0.300300, bitrate: 80296 kb/s
        Stream #0:0[0x1bf]: Data: dvd_nav_packet
        Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, smpte170m), 720x480 [SAR 8:9 DAR 4:3], max. 8000 kb/s, 29.97 fps, 29.97 tbr, 90k 
tbn, 59.94 tbc
        Stream #0:2[0xa0]: Audio: pcm_dvd, 48000 Hz, stereo, s16, 1536 kb/s
    [NULL @ 0x7fb0f2038600] Unable to find a suitable output format for 'foo.data'
    foo.data: Invalid argument

What is the "suitable output format", meaning what is the extension to use,
so the nav data can be extracted?

Thanks.