I am using the non-DVR Channels App on AppleTV.
I occasionally use the Quick Guide options button to select the “Show Stats” option which presents the live TV overlay showing various statistics.
I am writing today because I am trying to learn. And, ideally, perhaps troubleshoot a playback issue on a 3rd party OTA STB.
First, I would like to ask if there is an up-to-date manual/web page where the various fields on this stat screen are explained in detail.
If not, I am currently interested in a precise explanation for what 3 lines of attributes listed in the “Video” section represent and/or how they are calculated/determined/updated:
a. Dropped Frames: x (decoder) x (output)
b. Display FPS: xx.xxx (specified)
c. FPS: xx.xxx (specified) xx.xxx (estimated).
Currently, I am most interested in understanding how the “c.” “estimated” FPS value is calculated.
Following that, I would like to understand if/how having the “c.” “estimated” value exceeding the “c.” “specified” value might be related to apparently related increase in “a.” dropped frames “output”.
My interest in understanding these stats better has been triggered by 2 ATSC 1.0 RF channels in my OTA market. They apparently use Harmonic encoding solutions. And, their program streams (all MPEG-2) appear to be the only stations/program-streams in my market where “c.” “estimated” FPS values actually fluctuate and are not always equivalent to the “c.” “specified” value.
One station (let’s call it station “A”) is of particular interest. It carries 2x 720p60 and 5x 480i60 program streams. All MPEG-2. PQ is surprisingly good.
And, most importantly, the Channels app plays these back without a hitch!
What’s especially interesting is that the “estimated” FPS values on SD 480i program streams often bounce between 59.94 (also the “specified” value, as expected) all the way down to 23.976. Often, the “estimated” value bounces around between these two low/high bounds with estimated FPS values anywhere in between.
I suspect the station encoders are doing some kind of “optimizations” trying to preserve PQ and keep required bitrate as low as possible AND that these “optimizations” seem to trigger these estimated FPS readings. I’m wondering if the encoders are performing some type of “dynamic frame rate control”.
Finally, one reason I am trying to understand all this is because I suspect a 3rd party ATSC 1.0/3.0 STB is periodically having playback failures of these types of fluctuating estimated FPS ATSC 1.0 streams (like station “A” uses).
I’m suspecting the STB MPEG-2 decoder gets “confused” by the content of these program streams. Sometimes to the point where the playback app on the STB needs to be restarted.
Sorry for this lengthy post.
Would appreciate any/all assistance and/or comments.