词条 | Glits | |
释义 |
|filename = 2minGLITS.ogg |title = "GLITS test signal" |description = A 2 minute audio demonstration of the GLITS test signal, constructed in Audacity using instruction from this page. }} GLITS is an acronym for Graham's Line Identification Tone System, a test signal for stereo systems devised by BBC TV Sound Supervisor and Fellow of the [https://ips.org.uk/?post_type=fellow&p=5887 IPS] Graham Haines in the mid 1980s. It comprises a 1 kHz tone at 0 dBu (- 18 dBFS) on both channels, with interruptions which identify the channels.
This arrangement has an advantage over the EBU stereo ident tone in that each channel is explicitly identified as belonging to a stereo pair. The EBU Technical Document Multichannel Audio Line-up Tone (Tech 3304) defines stereo lineup tone as having an interruption in the left channel only, lasting 250 ms every 3 s. Multichannel GLITSThere is now an official EBU standard for a multichannel BLITS 5.1 channel ident tone which is also described in the Tech 3304 paper, along with an alternative film-style multichannel ident tone system for systems larger than 5.1 arrays. Blits plays a sequence of tones (based on the musical notes A and E) at -18dBFS on each channel in the AES channel format order (L, R, C, LFE, Ls, Rs), followed by an EBU-style ident on just the front left and right channels, again at -18dBFS and with four interruptions on the left channel. The four interruptions provides a unique confirmation that the stereo or mono downmix came from a 5.1 source and avoids any possible confusion with stereo EBU or GLITS downmixes. The final BLITS tone sequence is a 2 kHz tone at -24dBFS on all six channels – the lower source signal level ensuring that any derived downmixes remain close to -18dBFS. The alternative EBU multichannel ident tone follows a format more closely associated with the film industry. A sustained 80Hz runs on the LFE channel throughout the sequence. After a 3 second period of constant 1 kHz, -18dBFS tone on all main channels, each channel is identified in turn with a 0.5s pulse of 1 kHz tone, separated from its neighbours by 0.5s silence. The ident sequence starts at Front Left and continues clockwise through each available channel. The amount of time between the 3 second constant tone periods indicates the total number of channels in the system - e.g. a 7.1 system will have an ident sequence lasting 8 seconds. Snell & Wilcox have used the following on the embedded audio in their VALID8 (Video Audio Line-up & IDentification) equipment:
ReferencesExternal links 2 : Broadcast engineering|Test items |
|
随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识,基本涵盖了大多数领域的百科知识,是一部内容自由、开放的电子版国际百科全书。