[FFmpeg-user] FFmpeg concat outputs bad video file

Serguei Castillo serguei246 at gmail.com
Mon Oct 12 06:17:30 CEST 2015

Hi I have problema using concatenate, I concatenate 2 mpg files with
diferent resolution and when I put it on DVD It dosent work properly
but on the PC all is Ok What Happen?

On 09/10/2015, Paul B Mahol <onemda at gmail.com> wrote:
> On 10/6/15, Ryan Mirman <rsgm123 at gmail.com> wrote:
>> When I try to concat these 3 video files, it outputs a video with a too
>> short of a duration and way too high of a bitrate.
>> I am not sure if I am using ffmpeg the wrong way, if the audio is
>> corrupted, or if it is a bug with ffmpeg?
>> Here are the files,
>> https://mega.nz/#F!xsoGWIBA!1EQskrUQ1_09LenwhPawgw
>> These webm files have been recorded from webrtc through firefox on
>> archlinux.
>> The files used in each command are found in the linked mega folder.
>> This command is enough to demonstrate the problem I am having,
>>      ffmpeg -f concat -i list.txt -c copy output.webm
>> this gives an output file that is too short but has a very high bitrate.
>> (The log for this is concat_copy.log)
>> VLC may not play these videos at all, but firefox does for the most part
>> and I have been using GNOME mplayer.
>> In this, you should see a video that says it is 1 second long but plays
>> some audio after that but the video stops.
>> Also note that running
>>      ffmpeg -f concat -i list.txt output.webm
>> outputs a file with the same duration as before, but a much lower bitrate.
>> This should be similar to the last output video.
>> (The log for this is concat_transcode.log)
>> If you first convert the videos,
>>      ffmpeg -i 0.webm 0_fixed.webm
>>      ...
>> (the output for these are 0_fixed.log, ...)
>> and this above command with the corrected list file,
>>      ffmpeg -f concat -i list.txt -c copy output.webm
>> it outputs a file with the correct duration of 3 seconds and a normal
>> bitrate.
>> This should play like a normal video. (sorry for the crackly mic)
>> (The log for this is concat_fixed_copy.log)
>> It is possible that the audio was corrupted from recording, but even so
>> this behavior is not expected.
>> This does not happen from chrome on windows.
> The video & audio you concatenate must have same properties: widht,height,
>     pixel format, etc .. channels bitrate and so on.
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