VBR (Transcode) or VBR (CQ) on a Cut File of Same Size?

[Quamatek]

I have a .TS clip that I cut a few seconds from the beginning and few seconds from the end. I'd like to preserve the file as much as it can (as lossless quality as possible). Assume that all settings are the same and file size (of 500mb) are the same and not compressed from the source. Output to .M2T. I tried the following formats:

1. VBR (Transcode)
2. VBR (CQ)

I use several software to transcode and encode but for this project I'm using TMPGEnc Smart Renderer. On playback the file that did VBR (Transcode) appeared to have produced ever so slightly better quality. Maybe my eyes are just playing tricks on me.

First, am i right that if anything only the ends may need some encoding while the rest of the file can remain untouched? Secondly, is selecting VBR (Transcode) the right setting or should I have used VBR (CQ)?

[jagabo]

I don't use TMPGEnc. But if really is a smart encoder it only reencoded the cut GOPs at the start and end. The rest of the video should have passed through (assuming you didn't do any other filtering) without being touched.

[Quamatek]

Hi jagabo. Yes it only re-encoded the cuts at the start and end and passed through the rest. No other filtering was used. Now that I think about it the VBR (Transcode) and VBR (CQ) don't matter. Thanks for the reply

[jagabo]

Now that I think about it the VBR (Transcode) and VBR (CQ) don't matter.

It does matter for the reencoded GOPs at the start and end.

[Quamatek]

True. Being they were at the ends I meant to say that I'm ok with it. Since we're on the topic if a larger portion of the video had to be re-encoded, and all other settings and file size were the same, should I have used VBR (Transcode) or VBR (CQ)?

[jagabo]

Again, I don't know the particulars of TMPGEnc. But in general, you use bitrate mode when you need a file of a particular size (you know what the size will be but don't know exactly what the quality will be), CQ mode when you want a file of a particular quality (you know what the quality will be but you don't know the file size).

[Quamatek]

Makes sense. I adjust according to what my preferences are. Here's the description for the "Rate Control Mode" to give some reference:

CBR (Constant Bitrate)
Outputs the re-encoded parts at the bitrate displayed in the [Output Format] panel (Ex.: 4000 kbps)(for Smart Rendering, this is the original source clip's predicted average bitrate; for Rescue Clips, this is compliant with the Master Clip).
The allocated bitrate is the same for all re-encoded parts.
When in [Individual Clips (Smart Rendering Prioritized)] mode, the output is made compliant with the source clips' video bitrate.

VBR (Constant Quality)
Outputs the re-encoded parts at the maximum bitrate displayed in the [Output Format panel]. The allocated bitrate changes depending on the re-encoded parts' video data quantity. The ratio of bitrate allocation relative to the original source's video data quantity is set in the "Video Quality" setting.
When in [Individual Clips (Smart Rendering prioritized)] mode, the output is made compliant with the source clips' video bitrate.

VBR (Transcode)
You can select VBR (Transcode) only when the Smart Rendering process is applied to MPEG-2 video. When in linked output, this mode is not selectable when the Master Clip is an MPEG-2 video and links to a Rescue Clip.
VBR (Transcode) first performs the same processing as VBR (Constant Quality) in the re-encoded parts' range. Based on the set estimated bitrate, the outputted clip's total size is adjusted without re-encoding. The adjustment is performed with the Transcode Settings.