Audio Expert System Event Type | Protocol Solutions User Documentation

The following tables list the Audio Expert System Bluetooth, Codec, and audio events with description. Included in the tables is the event severity that can have three values: Information, Warning, and Error. The event severity will appear as icons and text in the Audio Event System once an audio stream has been captured. Refer to the Severity column in the tables below for an explanation of the severity types.

Event Type: Bluetooth Protocol

Event Type: Bluetooth Protocol

Protocol	Severity	Description
A2DP	Warning	AVDTP signal response received for unknown command.
A2DP	Warning	Unrecognized capability type
A2DP	Error	eSCO parameters requested.
A2DP	Error	Profile TX PDUs larger than available bandwidth for active A2DP Streaming interval.
A2DP	Error	Bitpool value does not match configured bitpool range.
A2DP	Error	Attempt to suspend inactive stream.
A2DP	Error	Configuration attempt using unsupported CODEC.
A2DP	Error	Incorrect AVTDP command length.
A2DP	Error	Unknown command Stream End Point Identifier (SEID).
A2DP	Error	A2DP stream configuration attempt using invalid CODEC parameters.
A2DP	Error	A2DP stream configuration request sent during active stream.
A2DP	Error	Audio data length does not match length header.
A2DP	Error	Incorrect A2DP SBC frame fragmentation.
A2DP	Error	A2DP SBC frame header contents do not match stream configuration.
A2DP	Error	Attempt to configure A2DP stream with unsupported configuration.
A2DP	Error	Reported A2DP stream capabilities do not contain mandatory features.
A2DP	Error	A2DP streaming L2CAP channel not disconnected after ABORT operation.
A2DP	Error	Fragmented AVDTP packet not terminated before sending next packet.
A2DP	Error	Invalid AVDTP transaction ID.
A2DP	Error	Missing AVDTP command response.
A2DP	Error	Unrecognized A2DP content protection type.
A2DP	Error	Attempt to configure delay reporting during incorrect stream state.
A2DP	Error	Attempt to open A2DP stream that has not been configured.
A2DP	Error	Attempt to close A2DP stream that is not active.
A2DP	Error	A2DP streaming channel created before configuration completed.
A2DP	Error	Configuration command contains invalid length parameter.
A2DP	Error	Configuration command contains invalid media transport format.
A2DP	Error	SBC CRC Error.
A2DP	Error	SBC invalid channel mode.
A2DP	Error	SBC invalid header.
A2DP	Error	Invalid AVDTP configuration parameter.
A2DP	Error	Invalid AVDTP stream state

Event Type: Codec

Event Type: Codec

Codec	Severity	Event	Description
SBC	Information	Codec Initialization	Codec session started
SBC	Information	Codec tear-down	Codec session ended
SBC	Information	Stream Re-configuration	Stream Re-configuration
SBC	Error	Incorrect Configuration Detected	SBC Codec detected a change in audio parameters
SBC	Error	Lost Sync	SBC Codec expected to find synch word: 0x9C instead found: 0x: typically due to corrupted data
SBC	Error	Bad Header	SBC Codec detected corrupted header: typically due to corrupted data
SBC	Error	CRC Failure	SBC Codec detected bad CRC: typically due to corrupted data
SBC	Error	No output	SBC Codec generated no output due to corrupted data
mSBC	Information	Codec tear-down	Codec Session Ended
mSBC	Information	Stream Re-configuration	Stream Re-configuration
mSBC	Warning	Packet Loss Concealment	mSBC Codec detected a bad frame and generated substitute data to compensate for it
mSBC	Error	Incorrect Configuration Detected	mSBC Codec detected a change in audio parameters
mSBC	Error	Lost Sync	mSBC Codec expected to find synch word: 0xAD instead found: 0x: typically due to corrupted data
mSBC	Error	Bad Header	mSBC Codec detected corrupted header: typically due to corrupted data
mSBC	Error	CRC Failure	mSBC Codec detected bad CRC: typically due to corrupted data
mSBC	Error	No output	mSBC Codec generated no output due to corrupted data when PLC not configured
AAC	Information	Codec initialization	Codec session started
AAC	Information	Codec tear-down	Codec session ended
AAC	Information	Bitstream type set	The bitstream type has been set. For Bluetooth, it should be LATM.
AAC	Warning	Single frame error, concealment triggered.	During decoding, a single frame error was detected which triggered built in concealment processing.
AAC	Error	Codec setting change	The codec has been re-initialized due to a setting change.
AAC	Error	Unframed stream error	A frame error was detected for an unframed stream. The codec is being reset in order to continue processing.
AAC	Error	Transport not initialized	The codec cannot be initialized for the given transport.
AAC	Error	Transport not supported	The selected transport is not supported. This could occur when an out of band LATM is selected opposed to in band.
AAC	Error	Transport failure	General failure in the transport.
AAC	Error	Transport error	This typically occurs when there isn’t any configuration information available.
AptX®	Information	Codec initialization	Codec session started
AptX®	Information	Codec tear-down	Codec session ended
AptX®	Error	Bad Data	Non-stereo data has been detected for incoming data stream.
LC3	Error	Invalid payload length	Codec received a frame with less data than configured
LC3	Error	Unable to decode a frame	Codec was unable to decode the data
LC3	Error	Invalid codec configuration	Codec configuration data is corrupted
LC3	Warning	LC3 codec applied PLC on this frame	Codec detected bit stream error and applied PLC to the frame

Event Type: Audio

Event Type: Audio

Test Mode	Severity	Event	Description
Non- Referenced	Warning	Low Volume Alarm	Warn the user that the volume level of the detected audio is below the best range for performing meaningful audio analysis. Alarm is initialized when volume level above the “Measurement Threshold” level is detected. Alarm is activated when the detected volume drops below the “Measurement Threshold” level for 10 consecutive 0.5 sec measurement intervals.
Non- Referenced	Warning	Clipping	Reports the detection of suspected distortion that occurs when the amplitude of a signal exceeds a digital systems ability to represent it accurately. Clipping is a type of amplitude distortion. The system reports a Clipping event when consecutive samples at the maximum value that can be represented by the digital system have been detected. The maximum value that can be represented is different depending on the number of bits per sample (i.e. bits of resolution) of the audio stream. The system limits the number of reported Clipping events to typically 10 to 20 per sec.
Non- Referenced	Warning	High Volume Alarm	Warn the user that the volume level of the detected audio is above the best range for performing meaningful audio analysis (i.e. above a level where the audio will likely become distorted). Alarm is activated when the detected audio volume is continuously above the high-volume threshold (see Figure 2) for 10 consecutive 0.5 sec measurement intervals (i.e. 5 sec total). The event will not be repeated again until the detected volume level drops below the high-volume threshold for 10 more consecutive 0.5 sec measurement connections.
Non- Referenced	Warning	Dropout	Reports the detection of an unusual brief silence period where the brief silence is preceded and followed by “normal” audio levels. A typical definition of Dropout is the short dramatic loss of volume typically caused by lost digital information. Root causes include transmission system errors resulting in lost data packets, transmission channel reconfigurations, bad sections of memory, processor overloads that temporarily interrupt the flow of information, and so on.
Non- Referenced	Warning	Glitch	Extremely large sample-to-sample audio amplitude transitions that have little probability of occurring within natural speech or music. Such dramatic changes would typically happen only in situations of dropped samples.
Referenced	Info	Test ID Found	Occurs when a valid Test ID has been recognized. A valid Test ID must meet the level, frequency, duration, and delimiter requirements. If any of these parameters do not match, the process is terminated and is reset to the initial conditions. Until a Test ID is successfully recognized, the system will continue to operate in Non-Referenced Mode; therefore, no events related to false starts are reported. This is because for arbitrary audio there is no expectation of any Test ID.
Referenced	Warning	Test Script Not Found	Occurs if a valid Test ID was found, but the script for that Test ID was not found. The system reverts to Non-Referenced Mode if this happens. This event should not occur if using a valid Reference Audio file provided by Frontline.
Referenced	Error	Invalid Test Script	This event is generated when an error occurs while accessing information in a script. This event should not occur if using a valid reference audio file provided by Frontline.
Referenced	Error	Synchronization Lost	Generated when after a successful Test ID recognition the system encounters unexpected frequencies or durations of audio segments while analyzing a received Reference Audio file. If this situation occurs, the internal segment tracking logic attempts to look forward and/or backward in the test script to determine if the currently measured characteristics are consistent with the previous or next segment of the script. If there is a match, the internal segment pointer is advanced or retarded appropriately, the Synchronization Lost event is not generated, and the audio analysis continues. However, if a match cannot be found, the system declares itself out of sync and generates the Synchronization Lost Event, terminates any active test script, and reverts to Non-Referenced Mode.
Referenced	Error	Unexpected Frequency	Reported when a measured frequency deviates from an expected frequency by a specific percentage (determined by the negotiated parameters of the over-the-air audio stream). The system knows the Reference Audio file that is being played on the Source DUT; therefore, the system knows which frequencies (tones) to expect at a given time.
Referenced	Error	Unexpected Level	Reported when the measured level at the start of a tone segment is not within tolerance. The tolerance is dependent on sample rate and bits per sample, but it generally is +/- 3 dB for speech and +/11 dB for music. The system knows the Reference Audio file that is being played on the Source DUT; therefore, the system knows which amplitude level to expect at a given time.
Referenced	Error	Unexpected Duration	Reported when a tone segment of the Reference Audio file is shorter or longer than expected. The system knows the Reference Audio file that is being played on the Source DUT and therefore knows how long a specific tone segment should last. If either a change of amplitude or frequency arrives either before or after that programmed duration, then the change is, by definition, unexpected. This type of audio impairment can be caused by lost or corrupted data, repeated data, faulty packet loss concealment algorithms, etc.
Referenced	Error	Amplitude Fluctuations	Reported if the system detects unexpected amplitude changes over a given interval. The test tones in Frontline’s Reference Audio files have a fixed amplitude level over their duration. Therefore, if the corresponding audio levels received over the air by the system fluctuates more than a specified level (this level is based on the received audio stream parameters), then the system generates an Amplitude Fluctuations event.
Referenced	Error	Unexpected Phase Change	Provides a fine-grained indication of lost or repeated energy. The system knows when a specific tone should be expected. During this interval, the system checks that the measured average frequency is the same as the expected frequency. If this is correct, the system will continue to monitor the instantaneous frequency. If the instantaneous frequency deviates sufficiently from the current average frequency, the frequency measurement state machine will reset and begin re-measuring. Typically, the outcome is the discovery of the next scripted (expected) frequency. However, another outcome can be that the same frequency as the previous average frequency is rediscovered, and this is reported as an Unexpected Phase Change event. Such phase changes are an indicator of losses of signal that do not result in amplitude dropouts, or signal substitution (repetition) of previous audio energy due to things such as “packet loss concealment” tactics.
Referenced	Error	Excess Noise	The Excess Noise event is reported when energy sufficiently above the “Silence Threshold” is detected during programmed segments of silence. Excess noise can indicate a poor analog audio chain with an inherently poor noise floor, glitches occurring during silence intervals, or codecs that do not transition to silence instantaneously.
Referenced	Error	Clipping	Reports the detection of suspected distortion that occurs when the amplitude of a signal exceeds a digital systems ability to represent it accurately. Clipping is a type of amplitude distortion. The system reports a Clipping event when consecutive samples at the maximum value that can be represented by the digital system have been detected. The maximum value that can be represented is different depending on the number of bits per sample (i.e. bits of resolution) of the audio stream. The system limits the number of reported Clipping events to typically 10 to 20 per sec.
Referenced	Error	CVSD HF Level Too High	Reported when a CVSD encoded audio stream is detected and there is high frequency energy above 4 kHz that is greater than -20 dBFS.
Referenced	Info	End of Test Event	Reported to indicate that the system has completed processing a test script for a Reference Audio file, and that the system has exited Reference Mode. This event is generated when the elapsed time from the start of test is equal to or greater than the scripted duration of a test. It is reached when the number of samples processed equals the number of samples associated with the test duration.

Clipping

The number of consecutive samples needed to qualify as a clipping event depends on both sample rate and number of bits per sample. Table 1 specifies the number of consecutive samples at the maximum value level that will generate a Clipping event.

Clipping Event Thresholds

Consecutive Samples	Sample Rate, Samples/sec	Resolution, bits
3	8000	16
5	16000	16
11	41000	16
2	64000	16
12	48000	16
24	96000	16

Dropout

Dropout events are reported when the average audio level (RMS) is initially above the Measurement Threshold, then falls below the Silence Threshold, and then quickly rises above the Measurement Threshold again. This approach largely disqualifies the natural inter-syllable silence and pauses that occur in natural speech but will detect gaps caused by dropped data.

The system does not report dropouts that begin at extremely low energy levels.

Glitch

The Glitch event is reported whenever an extremely large sample to sample amplitude transition occurs that has little or no probability of occurring within natural speech or music. As illustration, back-to-back +N, -N, …, +N, -N values (where N is any non-zero number), represents energy at the Nyquist frequency, or ½ the sample rate.

Neither speech nor music contain average energy levels at this frequency more the 20 dB below nominal. However, moderately large sample to sample changes in amplitude do occur, and these naturally limit how sensitive this measure can be configured.

The system uses back-to-back transition levels of 90 dB for music and 40 dB for speech as the threshold for reporting the Glitch event.

Such dramatic changes would typically happen only in the face of dropped samples and serve as an additional means of detecting gross abnormalities.