fenrir at elivagar.org
Wed Apr 25 21:58:31 CEST 2012
On Tue, Apr 24, 2012 at 01:22:23PM +0200, Peter B. wrote:
> FFv1's strength and major field of application seems to be in the
> archival domain rather than production or on-site recording. Therefore,
> its requirements to be able to support mid-stream changes seems
> questionable from my point of view.
> Information like TFF/BFF, aspect ratio, etc. must be provided somehow -
> and I am not sure where this information could be gathered from
> automatically (except field-order, maybe).
With MPEG codecs (MPEG-1/2, MPEG-4 ASP, MPEG-4 AVC), theses informations
(aspect ratio, field order and informations to create telecine streams)
are contained in the bitstream (some at the picture level, some at the
sequence level). As such, they can be extracted by the decoder and
provided to the encoder.
One use case for AR changes is for TV streams. On some TV channels, 16:9
was used for movies, and 4:3 for somes ads/old reportages.
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