Voice quality evaluation of various codecs

Rämö, Anssi

doi:10.1109/icassp.2010.5495201

Cited by 15 publications

(6 citation statements)

References 4 publications

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“…For example, wideband (WB) speech (50 to 7000 Hz nominal passband) has a documented higher perceived quality than narrowband (NB) speech (300 to 3400 Hz nominal passband) [1]- [3], but a transition from NB to WB speech coding is perceived as an impairment [4]- [6]. If the transition happens early enough in a speech recording, the value of the WB portion can exceed the harm of the transition, for a net improvement (relative to NB only) in overall speech quality.…”

Section: Background and Motivationmentioning

confidence: 99%

“…We designed a subjective speech quality experiment to measure the values of Qi and QCi,Cj(t, τ ) required in (2). We included six types of coding transitions associated with five different speech coding modes.…”

Section: Experiments Designmentioning

confidence: 99%

“…Note that the exact definitions of NB and WB vary by coder. Figure 4 of [3] and were measured with speech signals. Table 2 defines the six conditions with speech coding transitions used in this experiment.…”

Section: Experiments Designmentioning

confidence: 99%

“…Each transition involves shifting to a higher quality speech coding mode (based on earlier work and confirmed here). We selected AMR modes for Conditions 1, 2, and 3 after consulting [2] where various AMR-NB and WB coding modes were evaluated on a 9-point absolute quality rating (ACR) scale. On that scale, each of the exit coders measured about 1.4 quality units above the corresponding entry coder.…”

Section: Experiments Designmentioning

confidence: 99%

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When should a speech coding quality increase be allowed within a talk-spurt?

Voran

Catellier

2013

2013 IEEE International Conference on Acoustics, Speech and Signal Processing

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The value or harm associated with an increase in speech coding quality depends on the type of the increase as well as the temporal location of the increase in an utterance. For example, some increases in speech coding bandwidth can be perceived as impairments. The higher quality associated with the wider bandwidth can offset the impairment, but only if the increase happens early enough in an utterance. We present a subjective speech-quality experiment that qualifies these relationships at the talk-spurt time-scale for six different combinations of AMR and SILK speech coders. If a quality increase does not include a bandwidth increase, then, on average, it is beneficial only if it occurs in the first 2.8 seconds of a talk-spurt. If a quality increase includes a bandwidth increase, then it is beneficial only if it occurs in the first 1.8 seconds of a talk-spurt.Index Terms-AMR, SILK, speech bandwidth, speech coding, speech quality, subjective testing, time-varying speech quality BACKGROUND AND MOTIVATIONAvailable resources on modern voice networks vary with time. This, along with the mobility of many voice network users, results in dynamic resource availability for any given call. Service providers strive to provide a graceful degradation of speech quality when network resources become scarce during a call. When additional network resources become available during a call, it may be possible to increase the speech coding rate and deliver higher speech quality.But the effect of the quality transition must be considered. For example, wideband (WB) speech (50 to 7000 Hz nominal passband) has a documented higher perceived quality than narrowband (NB) speech (300 to 3400 Hz nominal passband) [1]-[3], but a transition from NB to WB speech coding is perceived as an impairment [4]- [6]. If the transition happens early enough in a speech recording, the value of the WB portion can exceed the harm of the transition, for a net improvement (relative to NB only) in overall speech quality. This was the case for NB-to-WB transitions at the 15 or 30 second point in a 60 second recording [4], [5]. But if the transition happens later in a speech recording, the shorter duration of the WB portion means that its value does not overcome the harm of the transition. This was the case for NB-to-WB transitions at the 45 second point in a 60 second recording [4], [5] or at the three-second point of a six-second recording [6]. In [6] we also experimented with gradual transitions (up to 2.5 seconds long) but found they did not mitigate the harm of the transition.Even quality transitions within a fixed bandwidth can be perceived as impairments. In [7], [8] short NB recordings with distinct quality levels were concatenated to form longer recordings and subjective scores were provided for both the short and long recordings.Analysis of these scores shows that when average quality is held constant, increases in quality variation lead to reductions in longterm speech quality.In [9] subjects evaluated three-second NB speech recordings with a low-high-l...

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Section: Background and Motivationmentioning

confidence: 99%

Section: Experiments Designmentioning

confidence: 99%

Section: Experiments Designmentioning

confidence: 99%

Section: Experiments Designmentioning

confidence: 99%

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When should a speech coding quality increase be allowed within a talk-spurt?

Voran

Catellier

2013

2013 IEEE International Conference on Acoustics, Speech and Signal Processing

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“…The difference stems from the fact that different telephony architectures use different audio codecs for voice data transmission. For example, while the G.711 codec used in high-quality ISDN links and in modern VoIP systems can generally achieve scores higher than 4, the GSM Full Rate voice codec only achieves a maximum score of 3.5 [17,48]. Further, it is likely that the conversion between different voice codecs has a negative impact on voice quality.…”

Section: Phonionmentioning

confidence: 99%

Phonion: Practical Protection of Metadata in Telephony Networks

Heuser

Reaves

Pendyala

et al. 2016

Proceedings on Privacy Enhancing Technologies

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Abstract:The majority of people across the globe rely on telephony networks as their primary means of communication. As such, many of the most sensitive personal, corporate and government related communications pass through these systems every day. Unsurprisingly, such connections are subject to a wide range of attacks. Of increasing concern is the use of metadata contained in Call Detail Records (CDRs), which contain source, destination, start time and duration of a call. This information is potentially dangerous as the very act of two parties communicating can reveal significant details about their relationship and put them in the focus of targeted observation or surveillance, which is highly critical especially for journalists and activists. To address this problem, we develop the Phonion architecture to frustrate such attacks by separating call setup functions from call delivery. Specifically, Phonion allows users to preemptively establish call circuits across multiple providers and technologies before dialing into the circuit and does not require constant Internet connectivity. Since no single carrier can determine the ultimate destination of the call, it provides unlinkability for its users and helps them to avoid passive surveillance. We define and discuss a range of adversary classes and analyze why current obfuscation technologies fail to protect users against such metadata attacks. In our extensive evaluation we further analyze advanced anonymity technologies (e.g., VoIP over Tor), which do not preserve our functional requirements for high voice quality in the absence of constant broadband Internet connectivity and compatibility with landline and feature phones. Phonion is the first practical system to provide guarantees of unlinkable communication against a range of practical adversaries in telephony systems.

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Challenges in Speech Coding Research

Gibson

2014

Speech and Audio Processing for Coding, Enhancement and Recognition

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Voice quality evaluation of various codecs

Cited by 15 publications

References 4 publications

When should a speech coding quality increase be allowed within a talk-spurt?

When should a speech coding quality increase be allowed within a talk-spurt?

Phonion: Practical Protection of Metadata in Telephony Networks

Challenges in Speech Coding Research

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