[Kdenlive-devel] Editing AVCHD h264/AC3 files in kdenlive

Dan Dennedy dan at dennedy.org
Sat Apr 18 18:50:35 UTC 2009

2009/4/17 Andre Madeira <amadeirabus at gmail.com>:
> Hello kdenlive-devel!
> My goal is to edit AVCHD (h264/AC3) files in kdenlive. The videos are

It is not yet ready.

> generated from my Panasonic HDC-SD1 camcorder and are all interlaced or
> 1080i. For what is worth, I can play these files properly on my linux box

Playing sequentially is one thing, seeking is another, and editing
requires seeking. In ffplay, try clicking around on the window. The X
axis determines the seek percentage. It is not clean. This was being
addressed a couple of months ago, and great progress was made;
however, the effort has stalled.

>   3) ffplay/ffmpeg (HEAD revs)
>       ~80% CPU w/ 1 core only. No A/V sync issue. No deinterlacing.
>       ./ffplay -skiploop 48 -threads 4 file.m2ts
> I understand kdenlive uses ffmpeg and that VDPAU support in kdenlive is not
> ready yet. However, I expect kdenlive to behave similarly to option (3) at
> least, but unfortunately the playback in the clip monitor is pretty choppy
> and nowhere near any of the options above.

The kdenlive monitor is a progessive consumer, and therefore will
incur a deinterlace operation - by default. Also, MLT is not optimized
for simple, straight playback to computer display. It converts the
video to a slightly different Y'CbCr (YUV) format more suitable to
processing (easier to adapt RGB-based code and algorithms) and for
output to a broadcast SDI video card (for which MLT was originally

> I tried recompiling kdenlive's src/recmonitor.cpp and added the skiploop and

-skiploop is a ffplay option, but MLT, like the ffmpeg utility, uses
the AVOptions. The corresponding AVOption is "skip_loop_filter" and
you need to set that property on the producer. The recmonitor.cpp
would only contain a consumer.

> threads option (above) with no success; i.e. the behavior is apparently the

You need to set the "threads" property on the producer (and make sure
ffmpeg was built with pthreads enabled). Kdenlive already exposes this
on the clip properties. Also, the kdenlive preferences lets you turn
off decoding B frames for H.264.


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