user5436: I have a large (~3GB) video file and I would like to trim just a few seconds at the beginning (~3s).
What would be the fastest way to do this without having to process all the video file?

user2836: You could try using a tool like VirtualDUB, but your options will depend on the type of file that you are working with.  Some files don't support arbitrary adjustment without atleast some amount of re-encoding.

user4943: Libav can do that as well, but it is not clear what you mean by 'process'. With avconv you can remux without reencoding, so you will still read the whole file and write it again, but will use only minimal processor power to split and then recombine the streams.
The format of the command can be along the lines of:
avconv -ss 3 -i in.mkv -c:a copy -c:v copy out.mkv

The results will depend on codec, since you cannot really copy all the codecs at any arbitrary point. IIRC libav will start at the next possible point in such cases, but that maybe a full second later (or perhaps even more, even though i didn't run into such things).
If you require an "in-place edit", and cannot afford even the harddrive load that will happen due to you reading and writing large files, then you should really provide much more information about the format (as much information as you have, but at least: container, streams, codecs for each stream).

user5600: Try this: 

Open the file in the Quicktime player -- it'll have to be Quicktime Pro.
Select the frames that you want to remove with the input and output markers.
Hit 'Delete.'
Then save as a 'self-contained' movie.


5436: <p>I have a large (~3GB) video file and I would like to trim just a few seconds at the beginning (~3s).</p>

<p>What would be the fastest way to do this without having to process all the video file?</p>
 2836: <p>You could try using a tool like VirtualDUB, but your options will depend on the type of file that you are working with.  Some files don't support arbitrary adjustment without atleast some amount of re-encoding.</p>
 4943: <p>Libav can do that as well, but it is not clear what you mean by 'process'. With avconv you can remux without reencoding, so you will still read the whole file and write it again, but will use only minimal processor power to split and then recombine the streams.</p>

<p>The format of the command can be along the lines of:</p>

<pre><code>avconv -ss 3 -i in.mkv -c:a copy -c:v copy out.mkv
</code></pre>

<p>The results will depend on codec, since you cannot really copy all the codecs at any arbitrary point. IIRC libav will start at the next possible point in such cases, but that maybe a full second later (or perhaps even more, even though i didn't run into such things).</p>

<p>If you require an "in-place edit", and cannot afford even the harddrive load that will happen due to you reading and writing large files, then you should really provide much more information about the format (as much information as you have, but at least: container, streams, codecs for each stream).</p>
 5600: <p>Try this: </p>

<ul>
<li>Open the file in the Quicktime player -- it'll have to be Quicktime Pro.</li>
<li>Select the frames that you want to remove with the input and output markers.</li>
<li>Hit 'Delete.'</li>
<li>Then save as a 'self-contained' movie.</li>
</ul>
