Re: Sox marker handling Was: Re: merging mono files

Jan Stary <[email protected]> writes:

>> > in that case I would propose to issue a warning and copy the markers
>> > from one source - this can be achieved without understanding the markers.
>> > A more elaborate solution could use both markers, but ommit markers
>> > which are too close together. This, however requires extracting and
>> > understanding the information of the markers.
>> 
>> As someone else already said it is not precisely known how sox handles
>> markers, and I don't feel that it should become a marker editing/merging
>> application.
>
> SoX ignores them when writing the output.
>
> Recently, new maintainers of SoX have kinda been established
> - do they have an opinion on this? I believe keeping the markers
> should not be much different from keeping the ID3 tags and other
> extras from the headers. (Not to play down the work to do.)

Preserving unknown chunks when the input and output file formats are the
same is of course fairly simple and sometimes useful.  However, there is
no way of knowing whether whatever processing was done invalidated the
information contained therein.  For example, if the sample rate was
changed, any reference to sample numbers would need adjusting.
Likewise, if the audio has been trimmed or padded, time references will
need shifting.  And so on.

The safe choice here is to add an option to pass through specific header
chunks.  That way, the user can request it if he/she knows it to be safe.

Copying ID3 tags is generally safe since very few, if any, are directly
dependent on the actual audio samples.  Of course, depending on what
processing has been done, calling it by the original title may no longer
be accurate, but it won't affect the correct downstream processing of
the audio data.

-- 
Måns Rullgård

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