Re: Restore/set aspect ratio header in DV files?

On Tue, May 26, 2009 at 12:14 PM, Richard Rasker <[email protected]> wrote:
> Op dinsdag 26-05-2009 om 09:52 uur [tijdzone -0700], schreef Dan
> Dennedy:
>> On Tue, May 26, 2009 at 5:57 AM, Richard Rasker <[email protected]> wrote:
>
> [snip Cinelerra messes up DV aspect ratio]
>
>> > The basic question is simple: is there a way to force a 16:9 aspect
>> > ratio onto a DV file -- iow: set the 16:9 aspect ratio header in the DV
>> > file? Kino's Edit -> Preferences -> Defaults offer an aspect ratio
>> > setting, but this is apparently overridden by the project/video file, so
>> > Cinelerra's faulty header settings are not changed.
>> >
>>
>> It depends upon your definition of easy and what you are willing to
>> sacrifice. :-) I see 2 ways: transcode with ffmpeg using the -aspect
>> option, or write a little C program using libdv to change the
>> metadata. With the transcode you will lose a little quality, but not
>> much, and it takes time and space. And at least you can use the
>> -threads option to make it faster.
>
> OK, the ffmpeg command seems to work fine already, thanks a lot!
>
> About the C program: I'd really like that solution, as it sounds much
> cleaner and faster than transcoding. But alas, I'm not really a
> proficient C programmer, to put it mildly. Nevertheless, I'd like to
> give it a serious try, if someone can start the wool on for me, as it
> were :-) And perhaps I could even supply a fix for Cinelerra ...
>
> So what DV metadata would need changing, exactly? Is this metadata

See
void dv_encode_metadata(uint8_t *target, int isPAL, int is16x9, time_t
*datetime, int frame);

where target is a frame of raw DV and the last param, frame, is a
number incrementing for each frame.

> contained in every frame, or is it just one header somewhere at the
> start of the DV file? And could you name an example of a source file
> which performs a similar operation on a DV file?

The libdv tarball contains reppm.c and recode.c. recode.c reads from
stdin and writes to stdout, which might provide a suitable model for
you, and reppm.c contains an example call to dv_encode_metadata().

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