Intermittent Missing Frames

rtbond wrote on 2/19/2010, 4:03 AM

We have encountered missing frames occurring intermittently when using Production Assistant (PA) to convert a set of H.264 MP4 files to Compressed RGB AVI files. The problem does not appear to be specific to a given MP4 source file, as rendering the MP4 from the timeline seems to always produce a correct render, and in fact often if the file is rendered again using PA it produces a good output.

The specific missing frame behavior is as follows: The first frame in the rendered Uncompressed AVI is actually the second frame from the source MP4 (hence the first frame from the MP4 source is missing in the PA produced uncompressed AVI) and a blank frame is inserted at the end of the rendered AVI (hence the frame count is the same as the source MP4)

As stated above, the PA behavior seems random, and if I run the same MP4 files through PA again, MP4 files that originally produced missing frame AVIs often produce correct uncompressed renders. As noted above, I have not seen this behavior when rendering the MP4 files from the timeline.

Comments, thoughts, suggestions?

This missing frame behavior is problematic as we are doing machine-based video quality assessment on the uncompressed AVIs and a missing frame throws off the analysis comparison that is done against the original source clip.

--
Rob.

Comments

JohnnyRoy wrote on 2/19/2010, 7:25 AM

The fact that the same file will render fine a second time seems to suggest that the PA code is functioning normally and the problem may actually be in the render step within Vegas. I would report this to Sony technical support so that the Vegas team can take a look at it and try and recreate it to determine what might be happening.

If you want to test further, it would be interesting to see if it's the load step or the render step that's causing this. One test might be to render each file twice (i.e., add the same render template twice and tell PA to make unique names). If one has black frames and the other doesn't, then it may be the render step and not the load step because both renders were from the same loaded file (i.e., the file was loaded once and rendered twice).

~jr

rtbond wrote on 2/19/2010, 8:02 AM

JR,

I will report to Sony.

Regarding your suggested test; how do I specify different output file names when using the same source file and render templates? I have not done much with changing output file names. I sure it is some simple.

Thanks!

JohnnyRoy wrote on 2/20/2010, 7:58 AM

> Regarding your suggested test; how do I specify different output file names when using the same source file and render templates?

Edit the template by pressing the Edit List... button. This will bring up the Render Formats window. Just above the list of file types is a dropdown list labeled Filename uniqueness. First select one of the file types in the list. Then select Add a numeric suffix (make unique) and press the Update button to update the selected file type. The list should now display "Numeric" in the "Filename suffix" column. Press OK to dismiss the dialog.

This will add a numeric sequence to the filename to ensure uniqueness. You can also select Add both the template name and number (make unique) if you have multiple formats that use the same file extension (i.e., DV, CineForm, DivX, Lagarith all use AVI as a filetype) or if you were rendering multiple bit-rates to the same filetype.

~jr