[FFmpeg-user] Concatenation of 50-100 files

[Paul B Mahol]

On 8/21/13, Dzung Nguyen <dzungng89 at gmail.com> wrote:
> On Wed, Aug 21, 2013 at 2:40 PM, Paul B Mahol <onemda at gmail.com> wrote:
>
>> On 8/21/13, Dzung Nguyen <dzungng89 at gmail.com> wrote:
>> > I realized that concat demuxer is the way to go. But one thing is that
>> it's
>> > very slow, to create a 40 min clip it would take hours. Anyway to
>> > improve
>> > the speed?
>>
>> Do not top post.
>>
>> You can improve speed if you do not transcode.
>>
>> >
>> >
>> > On Wed, Aug 21, 2013 at 11:42 AM, Dzung Nguyen <dzungng89 at gmail.com>
>> wrote:
>> >
>> >> You're right, it's the concat demuxer. So I guess concat protocol ( or
>> >> simply cat of files) would be more robust? I read that mpg files is
>> >> cattable, but after cat files the final video has no time information
>> >> (unseekable, can't play).
>> >>
>> >> This is how I create the subvideo:
>> >>
>> >> ffmpeg -loop 1 -f image2 -i image.png -q:v 0 out1.mpg
>> >>
>> >>
>> >>
>> >>
>> >> On Wed, Aug 21, 2013 at 10:46 AM, Paul B Mahol <onemda at gmail.com>
>> wrote:
>> >>
>> >>> On 8/21/13, Dzung Nguyen <dzungng89 at gmail.com> wrote:
>> >>> > I'm using ffmpeg concat protocol to join many subvideo files.
>> >>> > FFMPEG
>> >>> keeps
>> >>> > getting dropped packets and can't finish the process.
>> >>> >
>> >>> > ffmpeg -f concat -i list.txt -q:v 1 concated.mpg
>> >>>
>> >>> You are not using concat protocol but concat demuxer.
>> >>>
>> >>> Did you read documentation?
>> >>>
>> >>> >
>> >>> > Should I simply cat subvideo files, or concat in group of 10 and
>> >>> > then
>> >>> > concat again? In the first case, which encoding can be catted as
>> >>> > files?
>> >>> > _______________________________________________
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>> >>
>> >>
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>
> Sorry for the top posting. To avoid transcoding, I used -c copy command:
>
> ffmpeg -f concat -i list.txt -c copy concat.mpg
>
> But it turns out that there's a lot of errors and ffmpeg can't concat the
> files
>
> [mpeg @ 0x21b4a40] packet too large, ignoring buffer limits to mux it
> [mpeg @ 0x21b4a40] buffer underflow i=0 bufi=53885 size=133207
>
> Is it because when I create subvideo, I used the q:v 0 options, so the
> packet is too large?

-q:v does nothing with png, with png you can only change -compression_level.

>
> ffmpeg -loop 1 -r 1 -f image2 -i image.png -q:v 0 -r 29.97 -t 300 out.mpg
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