[FFmpeg-devel] Decoding AVCHD using multi-threaded code

Michael Niedermayer michaelni
Wed Dec 17 15:20:16 CET 2008

On Wed, Dec 17, 2008 at 11:11:09AM +0100, Jean-Michel Pour? wrote:
> Dear Friends,
> Are there any chances to parallelize decoding of this AVCHD file:
> http://www.kdenlive.org/videos/avchd-test-1.mts
> This is a typical camcorder file.
> Do you see any hope to parallelize or should be drop official AVCHD
> support in Kdenlive until multi-threading comes along?

The file only contains 1 slice per field, thus there is no hope to decode any
slices in parallel, unless 2 fields where decoded at once.
Decoding several fields and frames at once is being worked on.
Sadly ive not seem much activity there. If you care about it,
contact Alexander Strange. (if you provide some manpower (developers),
patches or (money to alexander) maybe things will move quicker)

The second thing is as has been mentioned that there is a problem with
timestamps and AFAIK everyone who looked at it had not been seen again.
If you are brave enough look at H.264 & H.222 (both freely available)
and implement some parser that fills in the timestamps that are not
stored in the source file.

also try -flags2 +fast which should provide a little more speed at the
expense of possible artifacts, and keep in mind you can maybe skip B
frames to speed things up further.

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

There will always be a question for which you do not know the correct awnser.
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