[FFmpeg-user] audio streams

[Rick C.]

On Nov 13, 2011, at 8:02 PM, Carl Eugen Hoyos wrote:

> Rick C. <rickcorteza <at> gmail.com> writes:
> 
>>> The -map option allows you to choose which stream(s) of the input file
>>> should be encoded.
>> 
>> Sorry here's the output below.  I guess there's no choice but to use the -map
>> option in this case?
> 
> [...]
> 
>> Input #0, mpeg, from '/Users/mahalko/Desktop/VTS_04_1.VOB':
>>  Duration: 00:23:56.44, start: 0.203422, bitrate: 5979 kb/s
>>    Stream #0.0[0x1e0]: Video: mpeg2video (Main), yuv420p, 720x576 [PAR 64:45
> DAR 16:9], 9800 kb/s, 25 fps,
>> 25 tbr, 90k tbn, 50 tbc
>>    Stream #0.1[0x20]: Subtitle: dvdsub
>>    Stream #0.2[0x21]: Subtitle: dvdsub
>>    Stream #0.3[0x80]: Audio: ac3, 48000 Hz, 5.1, s16, 448 kb/s
>>    Stream #0.4[0x81]: Audio: ac3, 48000 Hz, 5.1, s16, 384 kb/s
> 
> I agree with you that there are several signs that indicate 0x80 is the track
> most users want to encode. Unfortunately, I don't think it is so easy in the
> general case, so yes, you will have to provide -map afaict.
> (My guess is that 0x81 starts earlier with non-silent sound and this is why
> FFmpeg believes it is the more useful audio track. Just a guess.)
> 
> Carl Eugen
> 


Thank you for the reply Carl.  Yes 0x81 has a narrative and I believe it starts speaking before the "normal" sounds would come in with 0x80.  Just for me to learn what is the general rule FFmpeg uses to decide what audio track to use?  Thanks again!