我喺另外一個 forum 有回覆，喺喱部重覆一次部份回覆。

我覺得好多人都冇真正了解 MQA 背後嘅技術，係 business 方面普遍上都存在好大嘅爭議，當然喺 streaming 嘅 file 有好多良莠不齊嘅 version，我有睇到其實 Bob Stuart 咁多年以來一直都有喺 AES 發表多好多相關嘅 paper 都已經有唔少測試數據，當中亦包括 blind test 嘅數據等等，科學期刊嘅審查唔係咁容易就可以賣弄玄虛，其實佢嘅部份嘅技術喺 surround coding 上都已經應用咗好多年反而都冇乜人留意到。 我自己係 buy MQA 嘅技術，我亦認同今次 MQA 嘅 feedback。 我睇其實嗰條片嘅應用及測試方法都係有問題，直接截 digital signal data 展開嚟分析而唔係 analog analog 亦係對 MQA 分析嘅一個盲點及斷章取義，video 嘅 test pattern 個 encoding 本身已經係有問題及出現 warning，另外因為中間嘅 filtering corr. 亦係其中部份。 而我以前有遇過類似測試 vocoder 嘅經驗，普通 sweep tone 等平時常用嘅測試 audio h/w 嘅訊號係過唔到 vocoder，就算有時有啲頻段真過到嘅例子，解出嚟會變咗第種型態嘅失真，測試嘅方法好多時需要用原來嘅音樂訊號同輸出嘅音樂訊號做 de-convolution 等處理方法先到可以解讀到 vocoder 嘅 transfer function，唔係單單用 adobe audition 就咁截 digital signal 做 FFT 就可以分析到，不過我自己有都部 MQA ADC 遲啲得閒啲諗辦法測試吓。

feedforward correction 唔難做，我自己係用 roon dsp 嚟為 playback 器材當中包括 DAC、喇叭、xover 等等做 correction，但難就難在成個 signal-chain 有部份需要 apply 原先錄音器材嘅 ADC 等等，playback 器材變數及 correction 自己可以控制，但唔同錄音用唔同 ADC、mixer、DSP 每一部份都需要對應嘅 correction，喱個先係 MQA 要推嘅原因。

節錄自 MQA 嘅回覆:
As you may have seen in the messages returned from the service, the analysis phase of the encoder objected outright to 11 of the 14 files you submitted, with the message: “There was an error in this audio file. The MQA encoder was unable to encode it.”
The three that passed through presented these various warnings in combinations:

"Audio invalid ‐ Excessive alias ..."
"Audio invalid ‐ Input audio is predominantly 16 bits while file container is 24 bits "Input audio appears to have been wrapped",
"Input audio contains a band edge ..."
"Encode may not have worked as desired and may require further QC"

https://pastebin.com/2YfT6vfZ?fbclid=IwAR1KxxnBnAxQY36_tgopPrDv_WUbQckCExqE6zxCsJtF4M3d6LLbQNV-nls

https://www.youtube.com/watch?v=T7mq_RDiROI



一知半解嘅人實在太多，根本就冇花 effort 或冇能力去探究真相，爭議多亦好正常，就等如連 class a/ab 原理都未搞得清楚，更難識得用得好 class d amp。