Recommendation ITU-T P.1201 provides an overview of algorithmic models for non-intrusive monitoring of the audio, video and audiovisual quality of IP-based video services based on packet‑header information. The ITU-T P.1201-series of Recommendations addresses two application areas:
– ITU-T P.1201.1 specifies the model algorithm for the lower resolution (LR) application area, including services such as mobile TV.
– ITU-T P.1201.2 specifies the model algorithm for the higher resolution (HR) application area, including services such as IPTV.
The two ITU-T P.1201 model algorithms are no-reference (i.e., non-intrusive) models which operate by analysing packet header information as available from respective packet trace data, provided to the model algorithms in the packet capture format (PCAP). Further input information on more general aspects of the stream, such as the video resolution, which may not be available from packet header information, is provided to the model algorithm out-of band, for example in the form of stream-specific side information.
As output, the model algorithms provide individual estimates of audio, video and audiovisual quality in terms of the five-point absolute category rating (ACR) mean opinion score (MOS) scale. Further, diagnostic information on causes of quality degradations can also be made available.
Complementary to the ITU-T P.1201 models, there are further models described in the ITU‑T P.1202-series of Recommendations. These so-called ITU-T P.1202 models are bitstream-based video quality models. The main differences with ITU-T P.1201 can be summarized as follows:
– The ITU-T P.1201 models provide audio, video and audiovisual quality estimates, while the ITU‑T P.1202-only models provide video quality estimates.
– The ITU-T P.1201 models use packet header information, while the ITU-T P.1202 models exploit further bitstream information, such as coding-related information. As a consequence, the ITU‑T P.1202-models can be more accurate in their quality predictions. In turn, they require non-encrypted streams, to enable the access to payload information. Since the ITU‑T P.1202 models are more complex, they also require more computational power to estimate the video quality.