## 2 Materials and Methods
### Television Background
#### 2.1.3 OTT Service in the Managed Network  
The research has been conducted based on data collected from the Hiway TV [26] production system owned by the Polish telecom operator INEA [27]. TV services are only provided on the INEA's gigabit passive optical network (GPON), which is more reliable than the hybrid fiber-coaxial (HFC) network. TV features include live streaming, catchup, timeshift, video-on-demand, and given days back and forth recording. Live channels have different resolutions (SD, HD, and 4K) and bitrates (Table 2). A single channel can have multiple bitrate profiles, commonly from two to four, and resolutions from SD up to 4K. The SD and HD channels are encoded by H.264 codec with Main or High profile, level 4.1, 4:2:0 color sampling. The 4K content is encoded by H.265 Main 10 profile. The number of frames depends on the input received from the content providers. The frame number is passed through to the output. The TV operator distinguishes between ordinary and premium channels due to the importance of channels based on viewership, content consumption, or agreements with content providers.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Grade** & **Estimated Quality (ACR)** & **Impairment (DCR)** \\ \hline
5 & Excellent & Imperceptible \\
4 & Good & Perceptible but not annoying \\
3 & Fair & Slightly annoying \\
2 & Poor & Annoying \\
1 & Bad & Very annoying \\ \hline \hline \end{tabular}
\end{table}
Table 1: Absolute category rating (ACR) and degradation category rating (DCR) scale levels.  
The STB has Linux-based software that allows customers to create favorite channel lists, profiles with their settings, and multi-room options. Events connected to catchup, timeshift, or recordings inherit the parameters from the channel settings. Thus, in a single household, up to five devices can be established. Decoders can be connected to the optical network terminal (ONT) by Wi-Fi (802.11 b/g/n/ac) or ethernet cable.  
The live channels and timeshift, VOD, or nPVR events can be available with up to 4 video profiles (Figure 1). The 800 kbps (Figure 1a) and 1500 kbps (Figure 1b) are unacceptable to display on the TV screen. Those qualities may be sufficient for mobile. The 3000 kbps (Figure 1c) and 6000 kbps (Figure 1d) are qualities adequate to watch on TV screens. The highest video profile for a particular part of the content is treated as a reference bitrate.  
A black screen with a notification message indicates the stallings related to the buffer saturation (Figure 2). After the black screen appears, the STB can recover autonomously.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Channel Quality** & **Bitrate Range [kbps]** & **Resolution** \\ \hline SD & 800–2500 & 640 \(\times\) 480 \\ HD (ordinary channels) & 3000–6000 & 1920 \(\times\) 1080 \\ HD (premium channels) & 6000–8000 & 1920 \(\times\) 1080 \\
4K & \textgreater{}10,000 & 3840 \(\times\) 2160 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Channel profiles for the specific resolution.  
Figure 1: Different video profiles are available for the viewers: (**a**) 800 kbps, (**b**) 1500 kbps, (**c**) 3000 kbps, and (**d**) 6000 kbps. The video screens were derived from the Fiberhost S.A. video test file.