Saving incoming stream to a file

[tanir]

Dear All, I already know how to save an incoming stream to a file but my problem is slightly different. When VLC saves an incoming stream to a file, the saved file usually has higher quality than the 'real-time' displayed version. I believe the reasoning behind this is that, the server side sends video packets even if their playout deadlines have passed. When these packets are received at the client, they can be used for improving the quality of the saved file, but not for the 'real-time' displayed version. So the version viewed at the client side while streaming has lower quality.

I want both versions to have the same quality. Is there a way that I can save incoming video exactly as it is actually displayed in real time? I need this for my scientific research.

Regards,
Tanir

[dionoea]

You can dump video frames to images using the image video output (just append "-V image" to your command line) and then compare the images. Or maybe just increase the cache size on the client's size to make sure that it never misses late packets.

[yinglcs]

Hi,
Can you please tell me how do you save a incoming stream to a file using just command line parameters?

Thank you.

[dionoea]

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vlc <input> --sout file/ts://somefile.ts

[yinglcs]

I am using these parameter for transcoding ,and it works (#1):

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#transcode{vcodec=mp4v,vb=400,acodec=mpga,ab=128}:rtp{dst=127.0.0.1,port-video=1234,port-audio=1235,sdp=a.sdp}

But when I change it to this, it does not work (#2):

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#transcode{vcodec=mp4v,vb=400,acodec=mpga,ab=128}:standard{access=rtp,dst=127.0.0.1,port-video=1234,port-audio=1235,sdp=a.sdp}

From my understanding, I need to do this to save and boardcast a stream:

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#transcode{vcodec=mp4v,vb=400,acodec=mpga,ab=128}:duplicate{dst={standard{access=file, name='1.mp4'}, dst={standard{access=rtp,dst=127.0.0.1,port-video=1234,port-audio=1235,sdp=a.sdp}}}

and that is why I want to above #2 to work.

Please correct me if I am wrong.
Thank you.

[dionoea]

#2 has been deprecated in favor of #1 which is why it doesn't work anymore. And you're allowed to use rtp{} in duplicate too

[yinglcs]

Thanks for your help.

I have change my transcode parameter to this, per your advice:

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#transcode{vcodec=mp4v,vb=400,acodec=mpga,ab=128}:duplicate{dst={standard{access=file, name=file:///tmp/1.mp4}} , dst={rtp{dst=63.23.35.161,port-video=1234,port-audio=1251,sdp=file:///tmp/1.sdp}} }

The boradcast work, i.e. the part dest={rtp{.....}} works.

But I don't see any file get generated in /tmp/1.mp4. Can you please tell me why this part does not work:

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:duplicate{dst={standard{access=file, name=file:///tmp/1.mp4}}

Thank you.

[yinglcs]

I think I fix my problem by doing this:

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dst={standard{access=file, mux=mp4, dst=1.mp4}

I have have 1 question which is
If I do this, does that mean vlc will transcode the stream for me once? or twice (one for broadcasting, one for saving it to a file)?

Code: Select all

'#transcode{vcodec=mp4v,vb=400,acodec=mpga,ab=128}:duplicate{dst={standard{access=file, mux=mp4 dest=1.mp4}, dst={standard{access=rtp,dst=127.0.0.1,port-video=1234,port-audio=1235,sdp=a.sdp}}}

Thank you for any pointers.

[dionoea]

It will transcode it only once.

[yinglcs]

Thanks again.

I am using this argument to transcode from flv to mp4:

#transcode{vcodec=mp4v,vb=400,acodec=mpga,ab=128,width=176,height=144}

My question is why my final mp4 file is bigger (almost double) then my original flv:
original flv: 12430891
final mp4: 22409186

During the transoformation, I scale the video down (to 176X144). So I expect the mp4 file is smaller than flv.

Can you please tell me why?

Thank you.

[tanir]

The picture size is not the only determining factor for video size in bytes. You will have to reduce the transcoding bitrate (audio/video) if you want to reduce the mp4 file size.

[dionoea]

What video and audio bitrate did the original FLV file use? (You can view those in the "Stream and Media Info" dialog in VLC)