Question: What is the mandatory speech codec support requirement for a Transparent end-to-end Packet-switched Streaming Service (PSS) when narrow-band speech is utilized?
Option 1: AMR Wideband Speech Decoder with 8 kHz and 16 kHz sampling frequencies
Option 2: AMR Decoder for narrow-band speech with an optional upgrade to wideband
Option 3: G.711 Codec for both narrow-band and wideband speech
Option 4: EVS (Enhanced Voice Services) Codec for all speech types
Explanation: According to the specifications, when narrow-band speech is supported, the AMR decoder (operating at an 8 kHz sampling frequency, typical for narrow-band) must be supported. Wideband speech support (at 16 kHz) and thus the AMR Wideband Speech Decoder is conditional, based on whether wideband speech is supported. Therefore, the mandatory requirement specifically for narrow-band speech is the AMR decoder, with an implication that wideband support would necessitate additional codec support (AMR Wideband).