[Libav-user] Muxing to file with unknown frame rate

[Robert Jamieson]

>From: Libav-user <libav-user-bounces at ffmpeg.org> on behalf of Carl Eugen Hoyos <ceffmpeg at gmail.com>

>Sent: 12 April 2017 20:46 GMT
>To: This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.
>Subject: Re: [Libav-user] Muxing to file with unknown frame rate
>

>>2017-04-12 16:29 GMT+02:00 Robert Jamieson <bob_jam11 at hotmail.com>:

>> I am attempting to mux footage from a variety of webcams into standards

>> based files. The footage is spread over a large number of files (all from
>> the same camera). The files are a proprietary format containing the encoded
>> frames that came directly from the camera (in most cases it is H.264, MJPEG
>> or MPEG4 with G.711 or PCM16 audio). Audio is optional.
>>
>>
>> I have created a pipeline for processing the footage that comprises of a
>> reader for the files (this reads the frames and pushes them through the
>> pipeline), a file sync that picks a suitable file format (based on the
>> incoming video and audio formats) and writes the already encoded frames into
>> the file. I am purposely not using a transcoder to save processing time.
>
>Just curious:
>Why can't you use the FFmpeg executable?
>
>Or to say it differently: Is there an input sample file that is not
>supported by FFmpeg?

The files are in a proprietary format and are both encrypted and contain other data.

I'm also decoding for playback as part of a wider application.

>> This is working well with one exception, I can't tell what the frame rate is
>> ahead of time because I can't read the files before I process them.

>FFmpeg's mov muxer only supports cfr, so you have to know the
>framerate in advance.

I have done some tests and noticed that both VLC and WMP seem to be far more supportive of mp4 containers with vfr and playback without issue.

Ideally I would like to support other containers for flexibility and also allow for not re-encoding the data to increase performance but at the moment it doesn't look like I will be able to do that.

>Carl Eugen

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