- #32 [LaLaLam], 23-04-14 11:18#31,無聊師兄分享的投訴MQA事件十分有趣,值得細味和觀察,有關MQA這類形的投訴非常多,甚至有部份用家話某種類形的音樂是不適合用 MQA去編碼解碼的,例如用電子合成樂器,快速掃頻的效果器等,要測試和認証這方面的問題是否重覆性是十分困難的,是需要一個有權威性的學術機構去作第三方測試才能知道問題所在,尤其現代的 audio streaming係經過網絡去完成,而且普通家庭用的”non-deterministic networking”; 數碼訊息是經過無數的 server/router , time/frequency domain 上也存在大量非確定性,MQA的前途的確不太樂觀,反觀飛記在 80年代初已在 CD 規格訂立了類似HDCD/MQA 的編解碼(pre-emphasis / de-emphasis) 存在,到現在部份 CD ripper亦需要去處理呢個很少用的flag. 我手上其實也有頗多這類古老CD, 佢地都係用 14 bit AD/DA,所以需要用此壓縮/解壓的方法去擴展動態。
- #31 [無聊會員], 23-04-13 16:23
[#23]
LaLaLam兄, 謝謝解釋。
[#24]
wklie兄, 謝謝關於decoder說明。
講過decoder, 又睇下一個有趣嘅encoder故事. 呢位GoldenSound係Tidal嘅contributor, uploaded咗啲MQA encoded files上Tidal做testing, 點知比Tidal鏟files同account, 去Tidal同MQA投訴, response就哈哈哈. 呢位GoldenSound去咗Audio Science Review, disclose呢單嘢. 據呢位GoldenSound做嘅test同analysis, 出咗呢啲意見, 有興趣可以睇下, 對digital audio有D認識就會容易理解D, 因為有D似學術論文.
聲明: 本人從來未講過MQA是好是壞, 本人同LaLaLam兄嘅討論集中係接近消失嘅HDCD.
https://www.audiosciencereview.com/forum/index.php?threads/mqa-deep-dive-i-published-music-on-tidal-to-test-mqa.22549/
0:00 - Intro
1:15 - Summary of topics
1:47 - Pre-video clarifications
3:44 - What is MQA?
5:41 - How I got test files encoded in MQA
6:57 - MQA 44.1khz vs Native 44.1khz
8:14 - MQA HiRes vs Native 88.2khz
11:11 - Reduced Dynamic Range
11:47 - Does unfolding work? (Many MQA releases are just upsampled 44.1khz)
12:41 - No Lossless on tidal if track is MQA
13:47 - MQA "Authentication" means nothing
14:30 - MQA Upsampling filter is leaky
15:33 - Filter attenuation analysis
16:54 - HiRes unfolding analysis
18:53 - Full decode analysis
19:54 - Conclusion
21:19 - My Opinion, and testing cables
25:46 - Why are manufacturers supporting MQA?
27:13 - Best way to play MQA files
27:44 - ifi GTO filter is MQA
28:56 - MQA's response
37:02 - Credits/Thank you
0:00 - Intro
0:45 - 1: Removal of my tracks
1:17 - 2: MQA's claims of "Losslessness"
4:06 - 3: Provenance and the Blue Light
5:42 - 4: Real world music vs test signals
6:54 - 5: More Real world music vs test signals
8:20 - 6: MQA Encoder errors
9:42 - 7: MQA's feedback
10:23 - MQA Editing wikipedia page
12:25 - 8: MQA Adding distortion and aliasing
14:00 - Are MQA's screenshots fake?
16:07 - 9: MQA sound quality and deblurring
16:37 - 10: MQA encoder is only for musicc
17:03 - 11: Video Title
17:15 - 12: General comment
18:30 - Closing thoughts - #30 [jimmyihv], 23-04-12 23:19MQA is in debt too much and the future is not good. I think it is not worth to save it.
Besides Tidal will have Hi Res music and MQA will not beat Hi Res music at all.
最後修改時間: 2023-04-12 23:21:56 -
- #29 [kx14cp1], 23-04-12 11:31所以一隻無花的碟,一部讀取正確數據的cd唱盤,對普通cd或mqa cd嚟講一樣重要。步步高讀碟皇幾花都讀到,但有幾多信息係原本定估算出嚟就唔知。
- #28 [LaLaLam], 23-04-12 10:26這也是一個問題,CD Red book訂立的規格是八十年代的產物,從來沒考慮會有pseudo random noise coding (PRN) 例如MQA的存在,而 CD 本身的Cross-interleaved Reed–Solomon coding CIRC 當然不會顧及 PRN,sub-coding 是有機會互相影響的,兩者其實是需要有學術機構行出來做一個整體規劃才能完美化,而家 MQA 進入了 chapter 11, 相信會有大哥出來打救的,而家大哥中出PRN coding最多最成功的在東方,不過 MQA細眉細眼,應該不感興趣吧。
- #27 [DY2036], 23-04-12 09:36好少人談論就係如果因為隻碟花而導致訊號損失,噉響呢種情況之下MQA CD或者MQA CD Player會點樣做,對輸出音效會唔會有可聆聽嘅失真。
- #26 [wklie], 23-04-12 09:18#25: Although a few MQA partners adopted this wrong design in their streamers, it is clearly wrong because it will fail several scenarios.
The simplest examples are this:
1. Use a CD transport, connect SPDIF to MQA CD player - the FLAC tag is not passed via SPDIF. With this wrong design, the MQA CD decoding cannot be invoked. A correct MQA CD player will handle it (e.g. Esoteric K-01XD).
2. Use a computer to play a free download of 24-bit FLAC MQA to a USB MQA DAC. The computer software will decode the FLAC to PCM. There is no FLAC tag when sending the MQA PCM to the USB DAC.
最後修改時間: 2023-04-12 09:19:17 - #25 [LaLaLam], 23-04-12 08:10>... but that would be a design flaw.
Actually, this may not be a design flaw. Indeed, the MQA file structure is quite different from a normal LPCM file. Ref. Pic. below, a 24 bit LPCM is linear 24 bit count from LSB, However, the MQA coded 24 bit has to break into 8 bit + 16 bit with two different LSB and be processed separately. FLAC tag can be used as the function of the red arrow as shown. - #24 [wklie], 23-04-12 00:45#22: A correctly implemented MQA decoder will work on all lossless formats including WAV, FLAC, AIFF, ALAC and MQA CD. Some implementations fail without proper tag, but that would be a design flaw.
最後修改時間: 2023-04-12 00:46:52 - #23 [LaLaLam], 23-04-11 22:23>.... MQA file 用FLAC封装,又冇乜嘢原因?
如果是 end user,咁 MQA 用 flac 還是wav其實沒所謂,兩者都可以正常認到,音質分別也不大,不過 flac format本身有 Metadata tags, 可以包含歌名,封套 artwork 等和用甚麼 encoder (e.g. MQA or HDCD),所以如果用 music editor的話,咁 flac 的 tag 指向 MQA 本身既 metadata就變成必須,而且不會弄壞 MQA裏面隱藏了的data。 - #22 [無聊會員], 23-04-11 21:42#21
LaLaLam兄,
謝謝解釋.
Windows Media player 同 foobar2000 有 HDCD plug-in, 我知道但未用過. 很久很久前, 我有部 Audio Alchemy DDE v. 3.0 係有解HDCD功能, 不過未用過, 因為我冇HDCD碟, 又係很久很久前我有用 Masterlink 9600 自己整24bit CD玩,依家就絕大部分係file, up & down conversion 就一直都係部古董 dCS 972.
另外想請教 MQA file 用FLAC封装,又冇乜嘢原因? - #21 [LaLaLam], 23-04-10 19:17#20, 無聊師兄,MQA 的確跟 HDCD 理念接近,HDCD係90年代中的產品,佢係用左 digital audio 16 bit 的最低 LSB 的1bit 去 control 同辨認是否 HDCD, 通常這個 LSB在普通 CD係不停變化的 floor noise,HDCD就 hard code左做1, 於是佢地開發的那粒 pm100/pm200就會認到呢個不變的LSB就會著左 HDCD的指示燈,進入pm chip的解碼狀態,所以事實上 play HDCD係只有 15 bit, 但佢地粒 pm chip本身係 DSP,所以可以做多好多嘢,1.開動壓縮解壓程式(如下圖示),2.用特別設計的 dithering filter,於是佢地話兩者加埋等如20bit dac, dynamic range>115dB, 不過一般認為這只是一個 trick而已,這間公司最後俾 microsoft 買左,Windows player聞說還有 hdcd plug in, 同樣 foobar也有一個類似的解碼 plug in.
- #20 [無聊會員], 23-04-10 17:16[#14]
LaLaLam兄,
謝謝解釋.
以我理解, 以 MQA-CD 對 HDCD 計, 兩者技術理念相近, 都係利用果LSB 4bit做啲coding, 係一般CD機play, 部機就當標準CD去解碼播放, 唔理果有特別coding嘅LSB 4bit, 係有 MQA-CD or HDCD 嘅CD機play, 部機會認到啲coding, 行 MQA or HDCD, 意圖提高個resolution, 例如 HDCD 話可以有 20bit resolution, 不同係 MQA 行soft軟解果LSB 4bit做啲coding, 而 HDCD 行hard硬解果LSB 4bit做啲coding, 請教LaLaLam兄, 我嘅理解是否正確?
最後修改時間: 2023-04-10 17:26:56 - #19 [peter827], 23-04-10 17:06一切離開CD規格嘅最終大部份都總覺得差咗啲,可能無論規格幾高都已不同於製作上監製拍版嘅標準。
最後修改時間: 2023-04-10 17:06:39 - #18 [kx14cp1], 23-04-10 11:53其實係市場普及上cd係最普遍,新技術係最舊的cd機或最新有MQA解碼的cd機都可以播放到,生產同用家又唔洗特登再買新機,其實諗到lee個方法真係好聰明,只係將信息搬到本身唔用的空間。與其講個格式對原本個信式有無破損,不如諗下自己套音響又還原到幾多好過,同一隻碟點解人地到好聲d。
- #17 [VinylBear], 23-04-10 11:19我始終覺得 攞走咗本身的LSB 4 bits去用嚟support超高頻的頻段,音源的小小fine details始終都係會冇咗.
曾經在某個網站見過專家講, 可以用理論和數學計算得出, 24bit音樂的LSB 4 bits才是noise floor. 24bit音樂files裏面的LSB 4 bits已經等於或低於DAC本身的thermal noise, 所以听Hi-Res music 其實只用到20 bits. 言歸正傳 - 所以16 bit音樂裏面的LSB 4 bits其實不是noice floor, 是聽得到的. Thanks. - #16 [LaLaLam], 23-04-10 08:15Meridian Audio做 MQA呢個 part本身應該屬創新科技公司,其實佢本身的科研係有助音響工業的發展, 今次危機大概屬於 chapter 11那類,被政府接管保護,有幾年時間俾佢重組或等待白武士資金打救,而家受傷可能受瑞信/SVB危機所害吧。
- #15 [ilock], 23-04-10 07:58MQA 同HDCD 有異曲同工之妙
我估計結果下場都係一樣
今次meridian 又唔知會唔會收皮 - #14 [LaLaLam], 23-04-10 07:49的確如是,一般16bit digital audio 的 dynamic range 係 96dB, 但失去最低 LSB 4 bit就變左 12 bit 即是大約 72dB, 但 MQA話佢地攞左黎用既呢4個 bit本身用來做 HiRes(PRN) coding之外,更會拚合返16bit兼做埋 noise-shaped dithering (ref. 下圖),所以擴展到120dB, 達致人類聽覺極限,工程科學上是可以做到兼測量到,但事實上跟聽感又是另一回事。
- #13 [VinylBear], 23-04-10 06:31照咁講 MQA是loossy的 並不是 lossless. Lost咗LSB 4 bits...
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