The Stream+ has many output resolutions available.
When you initially set up your Stream+, the output signal resolution will default to Best/Automatic. This means that the Stream+ will communicate with your TV through the HDMI connection. It determines the highest resolution that the TV/display will process and uses that output resolution. In general, 'Auto' is the best choice.
The resolutions that the Stream+ can scale to/adapt to/output via the HDMI connection, are; 480p @60, 720p @60, 1080i @60, 1080p @24, 1080p @30, 1080p @60. Though it is common to refer to a display's resolution by just saying '1080p 60', that is short for 1920 Vertical lines x '1080 Horizontal lines x 60 frames per second. 1080p is much easier to say.
Most TV's sold these days, (2018) have native resolutions of 1080p 60HZ. However, 720p and 4k resolutions are also quite common. Displays with 720p native resolution, will normally be able to process 1080p signals, so even though the native resolution of the display is 720p, the Stream+ will output 1080p to that TV/Display.
When Stream+ is connected to a 4K, it will default to 1080p @ 60. If it is processing a 4k signal, then it will pass-through the 4k content.
You might find that when you have a 1280 x 720p 'native resolution'/'aspect ratio' TV/Display connected to the Stream+, that some images/programs look better than others. You might consider changing Stream+ the output resolution to match that resolution. (720p @ 60fps)
Another common 'aspect ratio' that is somewhat common on smaller displays is 1360 x 768p. This resolution was somewhat common as a computer resolution termed WXGA. These are often marketed as '720p' displays and likely include an HD15 port to be used with a computer monitor. Changing the setting in the Stream+ to 720p, may or may not look better than auto setting.
There are other considerations when choosing an output resolution. When receiving OTA TV antenna channels, there are 3 resolutions commonly used in broadcasting today.
- 1920 x 1080i. e.g. most CBS & NBC channels are broadcast in this resolution/aspect ratio.
- Setting the output of the Stream+ to 1080p will very likely produce the best image on a 1080P native resolution display, when watching a 1080i program.
- 1280 x 720p. e.g. most FOX and ABC channels are broadcast in this resolution/aspect ratio.
- Setting the output resolution of the Stream+ to 720p would likely produce the best image on a 720p native resolution display.
- 720 x 480p. e.g. most secondary channels, (e.g. 10.2, 10.3. Not 10.1) Standard Definition content is broadcast in this resolution/aspect ratio. This is the resolution (NTSC) used in the US prior to ATSC HD TV.
For a more in-depth definition/explanation about various video resolutions and aspect ratio's, you can find additional information here. Also, there are hundreds of internet sites that can help you understand. Wikipedia is just one example.