I am trying to get great results using a green screen. I've been experimenting with it for years.

I've seen many videos on the Internet, I tried many different lights.

I had a great desk top, some suggested to get a better video-card, better video cards wouldn't work in my computer, the manufacturer suggested to change my power supply.

Sick and tired of all this, I invested in a new computer with a "better video-card".

The computer is fast, has two drives, one is SSD .

In the old computer I have some great Universal Audio Effects, these audio effects are a little expensive and come with their own card. I opened the new computer to transfer the Audio effects card, I found out the new computer didn't have any open slots. I called Universal, they told me to send them all the computer's speck, I did.

They told me their effects were not compatible with the computer.

Now while editing I noticed on the preview window the lips are a little out of sync with the audio, I spent a lot of time to line up the tracks. I rendered the video it looks perfect!

I changed the audio buffer.

As I said, I am working with a green screen.

I have two video tracks, plus the video I use to replace the green.

I am recording a vocalist who plays keyboard.

I have two audio tracks from the video tracks.

I have 4 audio tracks recorded directly in the QSC Mixer/Audio recorder

in edit I copy the vocal tracks and add two more tracks

I use BCC Chroma Key, Color Correction and Smart Zoom Effects on two tracks.

On the Audio I use several effects such as Compress/Limiter, Reverb. Delay, EQ, ETC.

My equipment;

Sony Vegas Pro 16 (built 424)

Ace Predator Desktop

Intel 7-8700 3.20 GHZ, Installed ram 32 GB

Windows 10 home 64 Bit

NVIDIA GE FORCE GTX 1070

PRESONUS AUDIO BOX44VSL Interface

QSC AUDIO MIXER/MULTITRACK RECORDER

SASUNG 43" HD Television, I use a TV to get a better idea what the product will look and sound like on a television, plus the large size allows me to see more details, on a smaller screen I wouldn't have noticed the lips out of sync.

Another thing is puzzling. I use two camcorders SUNY HDR -AX 2000 and a considerably inexpensive ZOOM camcorder. The Zoom gives better results!

No matter how powerful your computer is, applying complex effects to it like green screen is going to slow things down a bit, especially on types of media that require more power to decode (this is why you notice some cameras working better than others).

If using Vegas 17, it can use your video card to decode the video, which can be set in the video I/O tab of preferences.

It has nothing to do with audio buffers or any of that, you're just stressing your CPU/GPU to its limits. You can get faster frame rates by either using proxies (right click on the clips in your timeline, select "create video proxy", make sure you have preview quality set to either "preview" or "draft" for enabling proxies), enabling GPU decoding (only works on HEVC or H264 media), or lowering the preview quality on the preview window ("preview - auto" is recommended).

Also make sure the GPU acceleration is enabled under the video tab of preferences.

I never noticed this on my old computer, I used the same amount tracks and effects, I just had some crashes, I was advised by Magix to turn off GPU acceleration. at the time I was using an earlier version of Vegas, I think was 12 Maybe now it's noticeable because of the larger screen. I tried lowering the preview quality, didn't work out well. Maybe something in the video card settings, I got check with the manufacturer.

Basing your output audio sync on the Vegas preview is a big mistake, because that is not where it happens. The encoder is where final sync delay is determined.

However, do not select "Microsoft Mapper" as your audio device in Vegas because it introduces more latency. Select your audio device ASIO drivers, often called "HD Audio" or "Direct Surround" or whatever.

Your final output, at sane bitrates, in a variety of players, is the place to make that kind of judgment. We rarely have a problem except at insane bitrates.

You can estimate your sync in preview by selectively prerendering sections you are interested in, but that is still but a preview.

Thank you for your answer,

I am aware that I can't base the final product on the preview, but one has to have some kind of reference to make a decision to add or not an effect. Actually I would say my preview is almost as good as final product.

I switch back and forth from the Presonus interface and the TV, The Presonus uses the ASIO driver

If I have time I will load the project in the old computer and see what happens, as stated before I never noticed this problem.

To line up the tracks I use a single note from the piano or just a sharp clap at the beginning of the song.

Prerendering your edited video is probably the best solution for you.

Remember also that everything will work better if your added audio tracks match your output parameters -- assumed to be 48KHz 16 bit. Giving the Vegas preview high-bit audio source to downsample will just add to latency and overhead.

We really didn't have this problem when everything was interleaved -- when the video stuttered, so would the audio!

I record at 24 bit. I basically just record myself playing the keyboard and singing, every day I learn something new. Usually I record my live performances, that part became easy, the green screen presents a challenge. This link is to a song I taped in my basement with the green screen.

Downsampling adds to overhead and may cause more latency during preview. Just copy your original 24 bit recording to a 16 bit 48 KHz file and place that on the timeline instead. Does that make a difference to your eyes and ears?

I will try that on my next project. I remember a long time ago there was a dispute over CD and MP3 quality many couldn't hear the difference.

Another thing I can do is to work the audio first and render it to a stereo track.

I tried different preview settings, on a large screen television there is a big difference.