What does "Use best video quality" achieve?

[dragnil]

Hello,
I'm new to Blu Ray and ConvertXto HD. So far I have it working well and I'm happy with the results. I should add that at the moment I am taking recorded HD TV programmes and burning them to a Blu Ray disc. I'm using Win 7 on a 4 core i-5 processor. However, I have 2 scenarios:

1. A TV broadcast on about 1 hour will take about 7 hrs 30 mins to convert at a frame rate of 2 - 3 per second.

2. Following Claire's advice I deselected "Use best quality video", confirmed that it was still set to 1080 Full HD and all other options were unchanged. The conversion was done in about a fifth of the time.

I played the result of option 2, comparing it with the original recording and had difficulty seeing any difference, can anyone explain what the option of Best video Quality is actually doing?

Clearly the aim with Blu Ray is to achieve the best image quality, but could I be chasing the last half percent which my old eyes cannot see? I am far from being expert in this field so if I've missed something obvious please forgive me.

[Copnm]

Hello dragnil,

Basically "Use best video quality" reads at a slower rate with extra parameters (settings, if you will) that help the encoder produce similar frames on output. I believe it uses the slowest (exhaustive) reading method for this.

Thanks for reading,
Neil M

[dragnil]

Hmm, So are we saying that if I have an HD input file there will be no real advantage to using the Best Quality setting? I'm trying to work out whether the overnight task is necessary, at the moment I can't see the wood for the trees. Thanks for your input.
David

[Copnm]

Hello dragnil,

It basically says what it means: If you want the best video quality, "Use best video quality". It will duplicate a picture closest to the original vs not using that setting. The biggest disadvantage would be that it's time consuming since it reads dramatically slow and looks for more details.

Thanks for reading,
Neil M

[dragnil]

Well I've done a trial by creating a BD disc with and without the "Best Video Quality"selected, all other options unchanged, and for the life of me I can't see any difference. I was hoping that Cedric might offer a few words of wisdom on this. Am I chasing the last half percent of quality (that my eyes can't show me) - because if that's the case the answer, FOR ME, is to save time and convert the faster way. Aside from this point I like the programme very much - good work!

[Copnm]

Hello dragnil,

You can compare the data between the 2 folders by using a program called MediaInfo (don't know if you're familiar with it). You'll basically compare the video files using that program and check the bitrate. The one with the "Use best video quality" selected should utilize more bitrate to achieve a better picture, ideally. But even with all this said, it's your eyes that you should believe. If it looks good enough for you, then stick with it.

Thanks for reading,
Neil M

[ckhouston]

The question of what the best video quality option does has been asked several times but the only response from VSO was Cedric's initial announcement that it would be added in http://forums.vso-software.fr/latest-be ... tml#p82558 -- specifically, "This option will use another "motion estimation" method (and some internal additional parameters), giving better video results (but will decrease conversion speed, you choose)"

I have never found a benefit to use this option either but decided to do a detailed analysis to try and unravel what it does. So I set up tests with several files having different characteristics. Then I used a program called Bitrate Viewer which analyzes the converted files and shows plots of bitrate and quantization factor versus time for all scenes.

I again found no real benefit in using this option after extensive analysis. Results were:

1. There is usually a small increase in bitrate (3% or less) that is applied more or less uniformly to most scenes regardless of their type or complexity. That should favor the more simple scenes slightly but I couldn't observe any difference for any scene checked. In fact, quantization factors also rose slightly which indicates a small, but still unobservable, decrease in quality, proving once more that bitrate is not the sole indicator of quality.

2. I could not detect any improvement due to better "motion estimation" either. That is difficult to analyze though because it would mostly produce better accuracy, not an observable quality change.

There is a reason for the default state of options so most users should stick with them unless they have a good reason to change. I do so personally except for conversions of mostly simple scenery like TV shows -- http://forums.vso-software.fr/encoding-q-a-t17863.html

BTW, don't assume that all HD TV broadcasts are of highest quality. They are if received directly with an outdoor antennae, but those from cable or satellite are usually compressed in order to offer hundreds of channels, there is a big difference.

[dragnil]

Thanks, CK, for that really clear and helpful comment. I'll continue to disregard the option and your findings are very close to mine. Thanks again.