Encoding SW / Writing application

[android]

I have some videos, I was checking their properties/info

Mostly videos properties/ info has,encoding sw Lavfxx.xx.xxx this line

What is the purpose of this line??
Mostly videos have this line and some videos don't have this line

If video can work fine without that line then why

[Selur]

What is the purpose of this line

It's there to record which libav version that was used to encode the video.

If video can work fine without that line then why

if a problem occurs with the encoding, it's easier to track down which library was changed,...
(there are tons of metadata/flags on videos which are not really necessary)

[ProWo]

Lavf = Libavformat, part of the ffmpeg framework.
More info here: https://ffmpeg.org/libavformat.html

[android]

It's confusing, I want an example to understand properly

If there's a x264 codec binary and aac library then they will just encode video in .h264 track0 and .aac track1 right??

Then lavf will needed to join both tracks in to single mp4 mov etc??

Does lavf contains all formats like mp4 mov etc??

[android]

(there are tons of metadata/flags on videos which are not really necessary)

Then it will take more space compared to those videos which don't have this data,

if a problem occurs with the encoding, it's easier to track down which library was changed,...

Compressors should have options to include this type of data before encoding or not to keep, because I think this type of data is for advanced users which is not usefull for normal users ,if any problems occurs in encoding then user will try again

[Selur]

Then it will take more space compared to those videos which don't have this data,

correct, but the space needed by those are neglectable

Compressors should have options to include this type of data before encoding or not to keep, because I think this type of data is for advanced users which is not usefull for normal users ,if any problems occurs in encoding then user will try again

You are in luck if you use open source compressors, you could potentially adjust the code to your whishes.
Most folks don't care about these few bytes and think that the work of those that wrote the 'compressors&co' deserves some mentioning.

[android]

It's confusing, I want an example to understand properly

If there's a x264 codec binary and aac library then they will just encode video in .h264 track0 and .aac track1 right??

Then lavf will needed to join both tracks in to single mp4 mov etc??

Does lavf contains all formats like mp4 mov etc??

Anyone explain this

[jagabo]

lavf is the multiplexer for the container format (mkv, mp4, avi, whatever). h.264 and aac are the codecs.

[Selur]

+ those elementary streams (.264, .aac might also already contain some nonessential data)

[android]

lavf is the multiplexer for the container format (mkv, mp4, avi, whatever). h.264 and aac are the codecs.

What is multiplexer

[jagabo]

lavf is the multiplexer for the container format (mkv, mp4, avi, whatever). h.264 and aac are the codecs.

What is multiplexer

https://www.merriam-webster.com/dictionary/multiplex

being or relating to a system of transmitting several messages or signals simultaneously

The audio and video data (and any other data) in the file need to organized in such a way that the player knows what's what and so that the data is easy to read during playback. That's what the multiplexer does. Different containers have different ways of organizing all the data.

For example, a video file may have one frame of video followed by enough audio to cover that frame. Then another frame of video and another frame's worth of audio. Etc.

[android]

The audio and video data (and any other data) in the file need to organized in such a way that the player knows what's what and so that the data is easy to read during playback. That's what the multiplexer does. Different containers have different ways of organizing all the data.

Then what is difference between a container like mp4 mov etc and a multiplexer like lavf??

I have also seen some videos info/property that their encoding SW/writting application was GPAC-2.2-rev0-gab012bbfb-ab-suite instead of lavf but container was mp4


Does it means that lavf is like a compiler or something like that?? Which compiles frames and audio into mp4 mov etc I can be wrong

[Selur]

In this context:
multiplexer = program that takes streams and packages them into a container
Different tools can add/remove/change container and stream metadata.
MP4Box for example is a tool from the GPAC project which usually adds the GPAC-.... into.

[jagabo]

Then what is difference between a container like mp4 mov etc and a multiplexer like lavf??

Containers are the specification of how to organize the data. lavf is a library that knows how to deal with those A/V files.

I have also seen some videos info/property that their encoding SW/writting application was GPAC-2.2-rev0-gab012bbfb-ab-suite instead of lavf but container was mp4

GPAC is another library for dealing with A/V files.

[android]

Does video editors like vegas pro ,adobe, kine master etc also use this library,

lavf gpac only packs streams in mp4 mov does it means they just copy pastes compressed streams by x264 ,aac etc and packs in mp4 mov etc

What are some other library like lavf gpac

[android]

If someone compiles his own x264 encoder from the x264 source code, and encodes a video using that encoder, will lavf and gpac be written in that too??

And also check

Does video editors like vegas pro ,adobe, kine master etc also use this library,

lavf gpac only packs streams in mp4 mov does it means they just copy pastes compressed streams by x264 ,aac etc and packs in mp4 mov etc

What are some other library like lavf gpac

[jagabo]

Does video editors like vegas pro ,adobe, kine master etc also use this library,

Probably not. Open source projects often come with limitations that aren't compatible with commercial software.

lavf gpac only packs streams in mp4 mov does it means they just copy pastes compressed streams by x264 ,aac etc and packs in mp4 mov etc

Yes. Though it's much more complex than "copy paste."

What are some other library like lavf gpac

I don't know.

If someone compiles his own x264 encoder from the x264 source code, and encodes a video using that encoder, will lavf and gpac be written in that too??

The h.264 and aac streams can be written to elementary streams. But if you want them packaged in an MP4 (or other) container you need to use a muxer. You can either write your own muxer or use a library.

[android]

Elementary streams what is it??

[jagabo]

Elementary streams are the native format for a codec's output.
https://en.wikipedia.org/wiki/Elementary_stream

[android]

Is it playable by video players

[jagabo]

some

[android]

Thanks for explaining

[jagabo]

Keep in mind that an elementary stream will have only one stream. So a h.264 elementary stream will only have video -- no audio, no subs, no chapters.

[android]

How can I extract elementary streams from containers and make it playable, i did lil bit research and found that mp4 have video track in mdat(am not sure about it) so I opened an video file in hex editor and deleted everything except mdat and saved as .h264 file ,but it isn't playing ,there's something am doing wrong or may be everything idk

[jagabo]

ffmpeg can extract the elementary stream:

ffmpeg -i input.mp4 -c copy -an output.264