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

[Henk D. Schoneveld]

On 30 Oct 2013, at 15:08, Richard llom <richard.llom at gmail.com> wrote:

> 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.
Maybe a different search phrase might help. ffmpeg how to or ffmpeg “-r” or something like that.ffmpeg “-r” yields 2.170.000 results
> 
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