I have source media that is a good quality. When I import into Vegas it loses quality and looks like it has a low bit-rate. It looks this way in both the preview window and final export.
Here is a video demonstrating the problem:
My specs:
Version: Sony Vegas Movie Studio HD Platinum 10.0
Processor
Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz
Video Card
AMD Radeon R7 200 Series
RAM
16 GB
Operating System
Microsoft Windows 7 Home Premium Edition Service Pack 1 (build 7601), 64-bit
Source of media? where does it came from?
Seems like WMV format you are using... I think this is codec issue...
Since the blocking artifacts are visible in the Vegas preview, render setting are not a factor. Download and install Mediainfo and post the properties of your source video. Someone will advise on any source video issues.
If the source video was an OTA capture from broadcast TV there could be stream errors that would affect Vegas but maybe not your player software. Consider running VideoReDo Quickstream Fix to repair stream errors.
If you load just the source video into a new Vegas project matching media properties, do you get the same blocky artifacts?
Some things to try in this thread: https://www.vegascreativesoftware.info/us/forum/why-does-my-rendered-video-look-bad-quality-troubleshooting-basics--103361/
If you have access to try a later version, see if that would work better. I think SVMSP 10 was prone to these issues in certain cases.