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又一個 TCP BBR 的測試結果

TCP BBRGoogle 發表的 TCP congestion control 演算法,是一個純伺服器端就能夠改善 TCP 壅塞處理的機制。在 Linux Kernel 4.9 之後被納入了。

Spotify 有大量資料要傳到使用者端 (像是音檔),剛好是 TCP BBR 改善的對象之一,實際測試後得到了很不錯的改善數據:「Smoother Streaming with BBR」。

Spotify 公佈的資料沒有提到平台,所以先稍微了解一下他的音質,也就是「Audio settings」這篇。

在 Desktop 是 160kbps/320kbps Ogg (Standard/HQ)。在 Web Player 則是 128kbps/256kbps AAC (Standard/HQ)。

行動平台部份比較複雜,在 iOS 上是 96kbps/160kbps/256kbps Ogg (Normal/High/Extreme),另外有 Automatic 自動調整的設定。在 Android 平台則是 24kbps HE-AACv2 (Low) 與 96kbps/160kbps/320kbps Ogg (Normal/High/Very high) 以及 Automatic。

而最後 Chromecast 則是 128kbps/256kbps (Standard/Premium)。

測試時可以發現 shutter (指跟不上播放速度) 的情況降低了 6%~10%,而且下載速度增加了 5%~7% (對於慢速的裝置改善更多,10%~15%):

Taking daily averages, stutter decreased 6-10% for the BBR group. Bandwidth increased by 10-15% for the slower download cohorts, and by 5-7% for the median. There was no difference in latency between groups.

而各地區的差異也可以看出來改善很多:

另外他們在測試時,剛好遇到秘魯的機房連外發生問題,結果意外發現 BBR 還是可以穩定在這種網路環境下運作:

In Peru, the non-BBR group saw a 400-500% increase in stutter. In the BBR group, stutter only increased 30-50%.

In this scenario, the BBR group had 4x bandwidth for slower downloads (the 10th percentile), 2x higher median bandwidth, and 5x less stutter!

Ubuntu 18.04 上可以直接設定 BBR,在 Ubuntu 16.04 則可以參考「Ubuntu 16.04 用 speedtest-cli 測試 TCP BBR 效能」這篇的方式升級 kernel 後設定 BBR。

OS X 接藍芽耳機要注意的地方...

Twitter 上看到 OS X 接藍芽耳機時的音質問題:

看了一些討論,看起來除了蘋果自己的耳機外,其他家的藍芽耳機不一定會開 AAC 或是 aptX。雖然現在沒有其他家的藍芽設備,但以後如果買了要注意一下...

Google 發表新的 TTS (Text-to-Speech) 技術 Tacotron 2

Tacotron 是 Google 發表的 TTS 技術 (i.e. 輸入文字,請電腦發音),而前一版的 Tacotron 的錄音可以參考「Audio samples from "Tacotron: Towards End-to-End Speech Synthesis"」,論文則是在「Tacotron: Towards End-to-End Speech Synthesis」這邊可以看到。

這一版的則是在 Twitter 上看到有人提到:

這一版叫做 Tacotron 2,錄音可以參考「Audio samples from "Natural TTS Synthesis by Conditioning WaveNet on Mel Spectrogram Predictions"」,論文在「Natural TTS Synthesis by Conditioning WaveNet on Mel Spectrogram Predictions」。

這次在錄音頁面的最下面提供了盲測 (人類與 Tacotron 2 的錄音),基本上已經分不出哪個是真人了...

Savitech (盛微) 的 USB 音效驅動程式會安裝 Root CA (被發了 CVE-2017-9758)

Hacker News 上看到 CERT 的「Savitech USB audio drivers install a new root CA certificate」提到 Savitech USB audio driver 會安裝自己的 Root CA:

Savitech provides USB audio drivers for a number of specialized audio products. Some versions of the Savitech driver package silently install a root CA certificate into the Windows trusted root certificate store.

出自「Inaudible Subversion - Did your Hi-Fi just subvert your PC? (原網站已經無法訪問,參考備份連結 https://archive.is/K6REr)」,CVE 編號是 CVE-2017-9758,最初是由 n3kt0n 提出的:「某單位 drivers silently install certificate in trusted root certificate authorities store [CVE-2017-9758]」:

Mitre assigned this exposure the identifier CVE-2017-9758, but was initially tracked by HITCON ZeroDay project as ZD-2017-00386.

有兩把 CA public key 被塞進去。雖然目前還沒有徵兆 private key 有外洩,但還是建議儘快移除:

There is currently no evidence that the Savitech private key is compromised. However, users are encouraged to remove the certificate out of caution. The two known certificates are:

SaviAudio root certificate #1
‎Validity: Thursday, ‎May ‎31, ‎2012 - ‎Tuesday, ‎December ‎30, ‎2036
Serial number: 579885da6f791eb24de819bb2c0eeff0
Thumbprint: cb34ebad73791c1399cb62bda51c91072ac5b050

SaviAudio root certificate #2
Validity: ‎Thursday, ‎December ‎31, ‎2015 - ‎Tuesday, ‎December ‎30, ‎2036
Serial number: ‎972ed9bce72451bb4bd78bfc0d8b343c
Thumbprint: 23e50cd42214d6252d65052c2a1a591173daace5

另外 Savitech 也放出了新版的 driver,不包含 Root CA:

Savitech has released a new driver package to address the issue. Savitech drivers version 2.8.0.3 or later do not install the root CA certificate. Users still must remove any previously installed certificate manually.

看了一下說明,看起來是當時為了支援 Windows XP 而做的,但微軟已經不提供驅動程式的數位簽章了,所以就只好這樣搞...

現有語音控制的安全性問題:使用聽不見的高頻下令

雖然相關的理論很早就有了,但上個禮拜放出來的論文完整實做出來,叫做 DolphinAttack,取自於海豚可以聽見人類所聽不到的聲音:「DolphinAtack: Inaudible Voice Commands」(這邊的錯字是作者造成的,submit 到 arXiv 的標題有錯,但論文內描述則是對的)。

無論是 Siri 或是 Google Now,或是其他的控制軟體,都設計成能接受多種不同語調的人,而這個部份目前放的都太寬,造成人類聽不到的區段也可以下令:

也可以看到成功機率很高:

應該會有些調整...

MP3 專利全數過期

看到有人提到,查了維基百科上面的 MP3 條目,看起來在 4/16 就全部都過期了:

The basic MP3 decoding and encoding technology is patent-free in the European Union, all patents having expired there by 2012 at the latest. In the United States, the technology became substantially patent-free on 16 April 2017 (see below).

If the longest-running patent mentioned in the aforementioned references is taken as a measure, then the MP3 technology became patent-free in the United States on 16 April 2017 when U.S. Patent 6,009,399, held by and administered by Technicolor, expired.

The three exceptions are: U.S. Patent 5,878,080, expired February 2017; U.S. Patent 5,850,456, expired February 2017; and U.S. Patent 5,960,037, expired 9 April 2017.

算是可喜可賀?

分析聲音模擬其他人講話...

這種黑科技愈來愈成熟啦:「Lyrebird - An API to copy the voice of anyone」。

Record 1 minute from someone's voice and Lyrebird can compress her/his voice's DNA into a unique key. Use this key to generate anything with its corresponding voice.

Demo 的地方直接拿這三個人惡搞:(這樣做沒問題嗎 XDDD)

Please note that those are artificial voices and they do not convey the opinions of Donald Trump, Barack Obama and Hillary Clinton.

而且是有能力做到即時轉換:

Our GPU clusters generate 1000 sentences in less than half a second.

Bose 販賣用戶隱私被告

Unroll 在旁邊燒的時候 (參考 Uber 戰火蔓延到 Unroll),Bose 也不甘寂寞決定跟上科技業的潮流:「Bose headphones spy on listeners: lawsuit」。

Bose 直接將他們 app 收集到的資訊拿出來賣:

Bose Corp spies on its wireless headphone customers by using an app that tracks the music, podcasts and other audio they listen to, and violates their privacy rights by selling the information without permission, a lawsuit charged.

這次打算控告的產品包括這些 (這邊提到的 Zak 是原告):

Zak is seeking millions of dollars of damages for buyers of headphones and speakers, including QuietComfort 35, QuietControl 30, SoundLink Around-Ear Wireless Headphones II, SoundLink Color II, SoundSport Wireless and SoundSport Pulse Wireless.

編號可以記一下,之後可以拿來追蹤:

The case is Zak v Bose Corp, U.S. District Court, Northern District of Illinois, No. 17-02928.

NieR: Automata 將會出 HiRes 版 OST

看到 moraNieR: Automata 將會出 HiRes 版 OST:「3/29「NieR:Automata」 Original Soundtrack ハイレゾ同時配信決定!」。

2/23に発売されたアクションRPG『NieR:Automata』のゲーム内BGM を収録した、「NieR:Automata」 Original Soundtrackが 3/29ハイレゾ同時配信になります!NieRシリーズはゲームサウンドの評判が高い事でも知られていますが、今作もプロデューサー 齋藤陽介、ディレクター ヨコオタロウ、サウンドプロデューサー 岡部啓一(MONACA)の完全監修による、NieRファン、ゲーム音楽ファン必携の一枚です。

這太棒啦~

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