-----Original Message-----
From: ddenn...@gmail.com on behalf of Dan Dennedy
>On Thu, Jun 5, 2014 at 9:28 AM, Hart, James
>> First, the original file testcase.mp4 was generated using VLC recording a
>> stream. The testcase.mp4 file will run find with VLC and preview correctly
>> using `melt testcase.mp4` and other video players.
>
> testcase.mp4 is variable framerate. MLT does not properly support
> variable framerate sources. I think it should be OK for simple,
> sequential processing, but it may have problems when it comes to
> seeking or choosing a framerate when not specifying a -profile (many
> variable framerate files indicate 1000 fps).
OK, I'll see if I can generate a constant framerate file for the input.
>> testcase.mp4 -consumer avformat:transcode-linux.mp4
>
> Why no encoding parameters or preset?
I guess I made the assumption the default producer and consumer would do the
correct
thing. In general MLT is awesome and has been kind in this regard.
In the implementation I do use presets and encoding options but I was trying to
do some
quick testing with the command line. Point understood though, I'll retry
things with
those set on additional testing.
>>
>> So problem 1. This file cannot be consumed and transcoded correctly at all
>> using linux. This is less important to me as I have to currently use
>> windows.
>>
>> Problem 2. The produced file in windows from this source doesn't work in one
>> of the most popular video players, VLC, for some reason.
>>
>
> I reproduced this using melt from Shotcut 14.06 and your command line.
> I do not know why VLC is complaining about the output MP4. However, I
> noticed that if I load testcase.mp4 into Shotcut and Encode using all
> defaults - not even choosing a preset - then the output plays fine in
> VLC. Adding "properties=x264-medium" also produces MP4 output that
> works with VLC. Why?
>
> First of all, running without a preset gives:
> [aac @ 0x10c97b000] The encoder 'aac' is experimental but experimental
> codecs are not enabled, add '-strict -2' if you want to use it.
>
> The MLT avformat consumer has code that automatically sets the strict
> option if you specify an experimental codec explicitly, and the preset
> sets the audio codec. Thus, using the preset makes audio in the
> output, and somehow that makes VLC happier. But you don't want audio;
> so add "an=1" to the command line. Now, VLC is back to complaining.
> :-( Well, the default video bitrate is something extremely low like
> 200 Kb/s, and this is 800x600 @29.7 fps! Let's make this less
> challenging and get some better quality by adding "vb=2M" to the
> command line long with the "an=1". Now, VLC plays fine and does not
> complain. A test using ffmpeg command line shows increasing the
> bitrate was not required to make output compatible with VLC, but I do
> not know why.
Thanks a bunch for digging into this. To summarize, It sounds like if I
make the input file a constant framerate and minimally setup the encoding
options
with a higher bitrate that may solve these issues.
I'll try it out. I'll also try it on my 'linux' install and report if it
fixes what I see there. If not, I'll tell you what distro and such has the
problem in case that is an unrelated bug.
Thanks again,
James
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