user25665: I am digitalizing Super 8 film with a dedicated Somikon scanner.
It outputs H264 - MPEG-4 AVC films in 4/3 (1440x1080).
When I open these films directly with VLC, there are displayed in 4/3, which is fine.
Then I add them in Sony Vegas Pro 12 to edit/modify them, but Vegas Pro believes that they are 16/9 clips: although the Project [Projet] and Visualization [Visualisation] fields are in 4/3, the Display [Affichage] is in 16/9 (600x338) by default:
I have to uncheck the Simulate the peripheral image ratio [Simuler le format d'image du périphérique] item to get back the original 4/3 aspect ratio:

When I render the project, Vegas generates a video in 4/3 with the right resolution (1440x1080), but the video player sofwares (VLC for example, see capture below) believe it should be displayed with a 16/9 aspect ratio.


In conclusion, the resolution is good all along, but the default aspect ratio is wrongly set to 16/9 by/in Vegas Pro.
Is there a way to avoid that in the first place? 
Or is there a way to correct it afterwards (once the rendered file is created)?

user25665: I did not manage to solve the source problem, but I found how to overcome the consequences.
It is indeed possible to edit the aspect ratio of the rendered video using ffmpeg:
ffmpeg -i <INPUT_FILE> -aspect 4:3 -c copy <OUTPUT_FILE>


25665: <p>I am digitalizing Super 8 film with a <a href="https://www.somikon.fr/produit/scanner-de-pellicule-pour-films-8-mm-et-super-8-2/" rel="nofollow noreferrer">dedicated Somikon scanner</a>.</p>

<p>It outputs H264 - MPEG-4 AVC films in 4/3 (1440x1080).
When I open these films directly with VLC, there are displayed in 4/3, which is fine.</p>

<p>Then I add them in Sony Vegas Pro 12 to edit/modify them, but Vegas Pro believes that they are 16/9 clips: although the <code>Project [Projet]</code> and <code>Visualization [Visualisation]</code> fields are in 4/3, the <code>Display [Affichage]</code> is in 16/9 (600x338) by default:<a href="https://i.stack.imgur.com/vFSvx.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vFSvx.jpg" alt="Display in 16/9"></a></p>

<p>I have to uncheck the <code>Simulate the peripheral image ratio [Simuler le format d'image du périphérique]</code> item to get back the original 4/3 aspect ratio:
<a href="https://i.stack.imgur.com/GmaqW.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/GmaqW.jpg" alt="Display back in 4/3"></a></p>

<p>When I render the project, Vegas generates a video in 4/3 with the right resolution (1440x1080), but the video player sofwares (VLC for example, see capture below) believe it should be displayed with a 16/9 aspect ratio.</p>

<p><a href="https://i.stack.imgur.com/JM0ig.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/JM0ig.jpg" alt="Correct resolution"></a></p>

<p><a href="https://i.stack.imgur.com/xBxUz.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xBxUz.jpg" alt="But wrong default aspect ratio"></a></p>

<p>In conclusion, the resolution is good all along, but the default aspect ratio is wrongly set to 16/9 by/in Vegas Pro.</p>

<p>Is there a way to avoid that in the first place? </p>

<p>Or is there a way to correct it afterwards (once the rendered file is created)?</p>
 25665: <p>I did not manage to solve the source problem, but I found how to overcome the consequences.</p>

<p>It is indeed possible to edit the aspect ratio of the rendered video using ffmpeg:</p>

<pre><code>ffmpeg -i &lt;INPUT_FILE&gt; -aspect 4:3 -c copy &lt;OUTPUT_FILE&gt;
</code></pre>
