-
MPEG-2 SD – getting smart resample to work
It took me a while to work out how to do this, so I thought it would be a good idea to share the info with other Creative Cow readers.
My out-of-date Sony DCR-SX20E only records to MPEG-2 format – it’s a bit of a pain to make Sony Vegas work properly with it.
First, do the obvious things – load up Vegas, load the MPEG-2 file, and go down to project properties. At the top right of the window, click on “match media settings”. Pay particular attention to the Width, Height, Pixel aspect ratio and Frame rate – also, note the Field order.
Vegas now “understands” your file.
MPEG-2 is a lossy format, and ideally you don’t want to render it multiple times, or the quality of your videos will suffer. If all you are doing is cutting and splicing a few bits of video together before putting the results on DVD or Youtube, you definitely want to avoid rendering multiple times. Apart from the quality loss, it will take a long time for the whole video to render, especially on older hardware.
Fortunately, there is a solution. Vegas “smart resample” works out which parts of your video don’t need to be rendered again, and integrates them with other parts of your video which you may have changed or added effects to. It’s a great time-saver.
Unfortunately, Vegas doesn’t advise you what your best possible render settings are in order to take advantage of “smart resample” – you have to figure this out for yourself. Luckily, there is a good free open-source program out there that can help you with this – google, download, and install the program called “MediaInfo”.
Open MediaInfo and click on the top left to find the file you wish to analyze,browse for it and load it. Go to the bottom right of the window and select “Tree”. This gives you a big list of all the properties of your file. Scroll down and you will see lots of information about your file – particularly useful are Bit rate mode (can be variable or constant), Bit rate and Nominal bit rate. Leave the program open for now.
Hopefully you already made a note of the Width, Height, Pixel aspect ratio and Frame rate! Now you can click on Vegas>File>Render as. With MPEG-2, our only choice is the MainConcept MPEG-2, so select this and go to Template. Select the option that most closly matches your product (fps, width, height, and pixel aspect ratio). In my particular case, it was “DVD Architect PAL Widescreen video stream”. Make sure in partcular that you choose a project matching your pixel aspect ratio.
If you wish, you can now go ahead and click “save” in the Render As window. If you see the magic words “No Recompression Required” in the preview window, then congratulations – no further changes are needed.
If, as is more likely, the video started slowly rendering, then cancel the render, go to file>render as, and make sure the template that you chose before is still selected. Now click “custom”. This will present a confusing list of options – don’t panic! Check each option against the information in MediaInfo. In my case, I had to change the “Field Order” from “Lower Field First” to “Upper Field First”.
Now the crucial information – bit rate! In my case, the bit rate was variable, and even MediaInfo could not tell me the maximum and minimum bit rates. My solution was to select constant bit rate instead, entering the “Nominal bit rate” value from MediaInfo (9,100,000). I clicked OK, saved the render and finally I saw the “No Recompression Required” text appear in the preview window. If your bit rate is constant already, I’m guessing that the same thing will work.
The only downside to converting variable bit rate to constant is that the files get a little bigger – in my case 20% larger. For me, it’s a small price to pay so that I can make full use of the “smart resample” function, but each Vegas user’s priorities are different.
Disclaimer: I am new to Vegas, so this little help guide is by no means definitive. If you happen to have the same problem that I did, hopefully it will help to guide you to a solution!
And if you know that there are mistakes in the above text, feel free to point them out to help other users. In particular, if you know how to smart resample variable bit rate MPEG-2 SD files without converting to constant bit rate, please add your thoughts to help me and other Vegas users 🙂
-
2 Replies
-
[Kate Morris] “Disclaimer: I am new to Vegas, so this little help guide is by no means definitive. If you happen to have the same problem that I did, hopefully it will help to guide you to a solution!”
Awesome tutorial! Thanks for charing with the community.
[Kate Morris] “if you know how to smart resample variable bit rate MPEG-2 SD files without converting to constant bit rate, please add your thoughts to help me and other Vegas users :)”
I found that if I used variable bitrate and set the max and average to the max and average in MediaInfo (in my case 9,100,000 and 7,700,000 respectively) it rendered variable bitrate without any recompression. Apparently the low setting doesn’t matter.
~jr
http://www.johnrofrano.com
http://www.vasst.com -
Thank you for the compliment John – just trying to give a little back to the community 🙂
Your tip works great – indeed, it doesn’t seem to matter what the low bit-rate is set to, so long as the maximum bit-rate (as described by Mediainfo) is set to the correct value.
One thing that interests me is that I can set the “average” bit-rate to pretty much any value I choose, and the “no recompression required” message still appears. If I set the average to something low (say 2,000,000), the file’s size is much smaller, but the quality is not as good.
Clearly there is some compression being applied in this situation, despite the “no recompression required” message and the extremely quick render time. In the interests of keeping quality as high as possible, I’ll probably keep using a CBR (constant bit rate) that is the same value as the maximum bit rate – I’m guessing that changing the average rate to the maximum bit rate in VBR (variable bit rate) would result in exactly the same video being produced.
Thanks for your help John, hopefully this thread can help others who encounter the same problem that I did.
Reply to this Discussion! Login or Sign Up