[Libav-user] This command take 2 minutes to render. Can it be quicker?

Steve Boyer steveboyer85 at gmail.com
Wed Jun 4 15:12:09 CEST 2014

On Wed, Jun 4, 2014 at 5:32 AM, Vijay Kanta <viju.kantah at gmail.com> wrote:

> Hey guys,
> I found out it's the H264 encoding that is really screwing up the cpu
> cycles, and not the audio. @carl, moving it down didn't help, it still says
> invalid command.
> I found out that h264 encoding takes up 20 minutes with music and srt
> combined for a 2 min random video clip.

That isn't surprising. That is why (and entirely my fault for not making it
clearer) I suggested copying the audio stream as well as copying the the
video stream (by using -c:v copy) as it already is in an MP4 compatible
format. I've never messed around with subtitles, part of the reason I was
asking for a sample mp3, mp4, and srt. What is the purpose of the -2 and
-strict options? Try removing those and see if you have any better luck. If
those don't work and are still unwilling to provide a sample, start with
omitting the subtitle portions to make sure that the streams are being
copied correctly, and build up from there.


> On Sat, May 31, 2014 at 1:24 PM, Carl Eugen Hoyos <cehoyos at ag.or.at>
> wrote:
>> Vijay Kanta <viju.kantah at ...> writes:
>> > ffmpeg -i music/qT0pdDhKxFDnfJHq2.mp3 -c:a copy
>> > -i video/HKp1ZpHbANT4dmGRC.mp4 -vcodec libx264
>> > -crf 23 -vf subtitles=subtitles/1718379803.srt
>> > -preset ultrafast -strict -2
>> > film/HKp1ZpHbANT4dmGRC.mp4
>> Move "-c:a copy" behind the last input file.
>> But please note that compared to H264 encoding,
>> audio encoding should always be fast, so the
>> speed difference between audio copying and
>> audio reencoding should be less than using
>> different x264 presets.
>> Carl Eugen
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