Does using AviSynth affect quality?

[FrozenInferno]

If you import a video into VirtualDub using AviSynth with minimal parameters, set the compression to direct stream copy and export it, will the quality be affected at all?

[Baldrick]

It will be saved as uncompressed video(=HUUUGE) if you use avisynth and direct stream copy.

[FrozenInferno]

It will be saved as uncompressed video(=HUUUGE) if you use avisynth and direct stream copy.

Oh, you're right. Hmm, let me put it this way. If you take an AVC file, throw it straight into VirtualDub and recompress it into Xvid, and then do the exact same with the same source file, but this time import using AviSynth (minimal parameters), will there be a difference in quality between the two resulting files?

[Baldrick]

Nope.

[AlanHK]

It will be saved as uncompressed video(=HUUUGE) if you use avisynth and direct stream copy.

Oh, you're right. Hmm, let me put it this way. If you take an AVC file, throw it straight into VirtualDub and recompress it into Xvid, and then do the exact same with the same source file, but this time import using AviSynth (minimal parameters), will there be a difference in quality between the two resulting files?

In both case you have decoded the video to a sequence of video frames and then reencoded when you save it.

An Avisynth source command just decodes the video from whatever format, creating a virtual uncompressed AVI file.

You can't do DirectStreamCopy unless you are saving in the same format as the input, which is true on neither case.

[FrozenInferno]

So AviSynth itself takes no part in the encoding/conversion equation whatsoever as long as no special parameters are specified? But when importing using AviSynth, doesn't the encoder use the AviSynth decoded version of the file as the source? Wouldn't that alter the process or at least result in a different outcome?

[AlanHK]

But when importing using AviSynth, doesn't the encoder use the AviSynth decoded version of the file as the source?

Yes

Wouldn't that alter the process or at least result in a different outcome?

No.

Decoding a file should end up with the same video frames no matter how you do it.
Encoding has quality differences; decoding there is only one (right) way to do it.

But usually the whole point of using Avisynth is to apply various filters and transformations, so of course if you do anything beyond a XXXSource("video file"), it will be different.

[FrozenInferno]

But when importing using AviSynth, doesn't the encoder use the AviSynth decoded version of the file as the source?

Yes

Wouldn't that alter the process or at least result in a different outcome?

No.

Decoding a file should end up with the same video frames no matter how you do it.
Encoding has quality differences; decoding there is only one (right) way to do it.

But usually the whole point of using Avisynth is to apply various filters and transformations, so of course if you do anything beyond a XXXSource("video file"), it will be different.

Gotcha, thanks for clearing it up for me.

[DarrellS]

But usually the whole point of using Avisynth is to apply various filters and transformations, so of course if you do anything beyond a XXXSource("video file"), it will be different.

Which is why I hardly ever use Avisynth anymore. With all the new input plugins and the newer versions of Virtualdub, there isn't much need for me to use Avisynth.

I don't think I even reinstalled it after my last reformat.