[FFmpeg-user] Increase video speed via framerate change?

[Richard llom]

Henk D. Schoneveld wrote:
> On 30 Oct 2013, at 13:20, Richard llom wrote:
>> I have an video with 4 fps, I want to speed this up (time lapse), but
>> also increase the framerate, so I thought:
>> ffmpeg -i input.ogv -r 12 output.webm
> You’ll have to apply a little more thought to this. You have to encode, so
> tell ffmpeg which encoder library to use. ffmpeg -i file -c:v libx264
> chooses libx264 as encoder library. 
Isn't that detected automagic? I got a working result without specifying the 
encoder.
> Further you have to tell ffmpeg what
> the input frame rate is AND what output framerate you want it to become.
Ok, I tried with
ffmpeg -r 4 -i out-1.ogv -frames 14000 -r 16 output.ogv
and it works now as I expected it.

However, the result is very ugly, lots of distortion and noise... :-(

BTW:
The input file was created by recordmydesktop.
Before encoding ffmpeg warns me:
[ogg @ 0x1b087e0] Header parsing failed for stream 0
[ogg @ 0x1b087e0] Broken file, keyframe not correctly marked.
    Last message repeated 2 times
[ogg @ 0x1b087e0] max_analyze_duration 5000000 reached at 5000000

and during ffmpeg encoding I get lots of:
Broken file, keyframe not correctly marked.ime=00:10:56.81 bitrate= 
201.4kbits/s dup=7881 drop=0 

is there something I can do about?

richard


> Search the web for examples.
I found the ffmpeg Documentation site not so helpful, is there a good site 
out there? Searching for "ffmpeg examples" didn't yield any good either.