用 Machine Learning 改善 Streaming 品質的服務與論文

Hacker News 上看到「Puffer」這個服務,裡面利用了 machine learning algorithm 動態調整 bitrate,以提昇傳輸品質。

測試得到的數據後來被整理起來一起放進論文:「Continual learning improves Internet video streaming」。

在開頭介紹了 Fugu 這個演算法:

We describe Fugu, a continual learning algorithm for bitrate selection in streaming video.

而 Puffer 就是實驗網站:

We evaluate Fugu with Puffer, a public website we built that streams live TV using Fugu and existing algorithms. Over a nine-day period in January 2019, Puffer streamed 8,131 hours of video to 3,719 unique users.

這個站台提供了許多真實的頻道進行測試:

Stream live TV in your browser. There's no charge. You can watch U.S. TV stations affiliated with the NBC, CBS, ABC, PBS, FOX, and Univision networks.

可以看到 Fugu 的結果很好,比起其他提出的方案是全面性的改善:

這邊是用 WebSocket 測試,並且配合了不同的 TCP congestion algorithm,沒有太考慮額外的計算成本...

用 NN 演算法重製 Full HD 版的 Star Trek: DS9

看到「Remastering Star Trek: Deep Space Nine With Machine Learning」這篇,裡面用了類神經網路演算法,將本來只有 480p (SD) 的 Star Trek: DS9 升到 1080p (Full HD) 的版本,而且看起來效果還不錯...

意外的看到有人拿 Star Trek 的材料來玩... 依照作者的說明,DS9 一直沒有 Full HD 版的其中一個原因反而是因為「數位化」了。使用類比膠卷的母帶可以透過更高規格的重新掃描而得到高畫質版本,但 DS9 的母帶似乎已經是數位版了,所以反而造成無法透過重新掃描的方式取得 Full HD 版本:

While you can rescan analog film at a higher resolution, video is digital and can't be rescanned. This makes it much costlier to remaster this TV show, which is one of the reasons why it hasn't happened.

現有的 upscale 技術主要都還是以圖片為主,所以作者本來以為對於動態畫面的處理會遇到問題,但蠻意外的超出預期,從影片可以看出來:

看起來之後的 remaster 版本有可能可以靠這個方法先做初步,然後再讓人進去修?

Twitch 用 VP9 直播...

Twitch 整理了一篇「How VP9 delivers value for Twitch’s esports live streaming」,說明他們用 VP9 的經驗談。

裡面有很大的篇幅是在講 VP9 與 H.264 的比較,不過這兩個用的技術就已經不是同一個年代了,沒有進步的話就不用出來玩了...

裡面有講到一些有趣的東西,像是提到是用 FPGA 即時壓縮:

In this article, we will show that the FPGA-based real-time VP9 encoding can deliver at least 25% bitrate savings compared to the highest-quality H.264 encoders deployed in Twitch’s production today.

然後提到 1080p60 至少省了 25% 的頻寬 (這邊應該是相較於 H.264):

VP9’s Compression Efficiency for Live 1080p60 Encoding: We Can Achieve At Least 25% Bitrate Savings

查了一下,在桌機上的瀏覽器都差不多支援了:

VP9 is implemented in these web browsers:

Chromium and Google Chrome (usable by default since version 29 from May and August 2013, respectively),
Opera (since version 15 from July 2013),
Mozilla Firefox (since version 28 from March 2014),
Microsoft Edge (as of summer 2016).

行動裝置的話 Android 4.4+ 有支援,但在 iOS 上沒有支援...

整體看起來普及率算是不低,可以引入當主力 codec 降低頻寬成本,當設備不支援 VP9 時 (應該只有 iOS 透過 Safari 觀看的情況) 就用 H.264 stream 提供服務。

Netflix 在 Time Series Data Storage 上的努力...

在「Scaling Time Series Data Storage — Part I」這篇看到 Netflix 在 Time Series Data Storage 上所做的努力...

因為應用在寫多讀少的場景,所以選擇使用 Cassandra,遇到瓶頸後把常寫入的與不太會改變的拆開儲存,並且用不同方式最佳化。包括了 cache 與 compression 都拿出來用了...

不知道他們內部有沒有評估 ScyllaDB 的想法...

去電視廣告的服務又來了...

看到「Plex’s DVR now lets you skip the commercials… by removing them for you」這篇文章,介紹 Plex 要推出去電視廣告的服務...

維基百科上的介紹比較清楚:「Plex (software)」,主要有兩個元件組成,media server 與 player:

  • The Plex Media Server desktop application runs on Windows, macOS and Linux-compatibles including some types of NAS devices. The 'server' desktop application organizes video, audio and photos from your collections and from online services, enabling the players to access and stream the contents.
  • The media players. There are official clients available for mobile devices, smart TVs, and streaming boxes, a web app and Plex Home Theater (no longer maintained), as well as many third-party alternatives.

然後這次要推出的功能是直接在錄影的時候把廣告拿掉:

Plex confirmed it’s rolling out a new feature that will allow cord cutters to skip the commercials in the TV programs recorded using its software, making the company’s lower-cost solution to streaming live TV more compelling. Unlike other commercial-skip options, Plex’s option will remove commercials from recordings automatically.

這讓我有些印像... 當年 TiVo 也有類似的功能,不過文章裡有提到 TiVo 是提供 skip 而非直接拿掉:

The new feature works by locating the commercials in your recorded media. It then actually removes them before the media is stored in your library. That sounds like it could be even better than TiVo’s commercial skipping option, for example, because you don’t have to press a button to skip the ads — they’re being pulled out for you, proactively.

不過主要是認識了 Plex 這個軟體... 如果是電視兒童的話應該用的到 XD 台灣目前的電視節目好像看的比較少...

在北美盜版 IPTV 產生的流量比 BitTorrent 還多

算是前陣子的新聞,在北美地區的盜版 IPTV 流量比 BitTorrent 的流量還多:「IPTV Piracy Generates More Internet Traffic Than Torrents」。

During peak hours, 6.5% of all downstream traffic on fixed networks is generated by TV piracy services.

To put this into perspective; this is more than all BitTorrent traffic during the peak hours, which was “only” 1.73% last year, and dropping.

如果把影音網站都考慮進去,最大的還是 YouTubeNetflix 這兩個啦,不過盜版的量也不小...

然後也有把最大的量分析出來,這裡面最大的量是 Indian Star Plus HD,應該是印度裔或是印度籍的人看家鄉的東西?

The most viewed of all in North America, with 4.6% of all pirated TV traffic, is the Indian Star Plus HD.

不過 Sandvine 一直都有方法分析整個北美流量,讓人感覺不太舒服...

Netflix 在美國漲價

Okay,所以 Netflix 在美國的價錢漲了:「Netflix Is Increasing Its Monthly Subscription Cost」。

基本版不變:

The basic streaming plan, which only allows for streaming on only one screen at a time, will remain at $7.99 a month.

雙螢幕版漲 $1 變成 $10.99:

The company’s most popular plan — which allows customers to stream titles on two devices with a single account — will increase by $1 to $10.99 a month.

四螢幕版漲 $2 變成 $13.99:

The premium plan — which allows customers to use the same account for four screens at once — will increase by $2 to $13.99 a month.

紐約時報的說明是因為自製成本增加,如果是這樣的話,其他地區也應該有可能會找機會漲?

The price hike arrives as Netflix continues to increase production of original TV and movie content. The company said that by the end of the year it will have spent around $6 billion for original content in 2017. In August, Ted Sarandos, Netflix’s chief content officer, told Variety that the company planned to spend about $7 billion for original programming next year.

歐盟對於盜版是否帶來傷害的研究

歐盟在 2014 年做了關於盜版與銷量的研究,結果一直被壓到最近才發表出來 (於是就大概可以猜到結論了...):「EU Piracy Report Suppression Raises Questions Over Transparency」。

“In general, the results do not show robust statistical evidence of displacement of sales by online copyright infringements,” the study notes.

甚至:

The study found that piracy had a slightly positive effect on the videogames industry, suggesting that those who play pirate games eventually become buyers of official content.

另外也描述了現有電影與 TV-series 定價策略偏高:

“Overall, the analysis indicates that for films and TV-series current prices are higher than 80 per cent of the illegal downloaders and streamers are willing to pay,” the study notes.

難怪被壓著...

EFF 因 DRM 退出 W3C

EFF 一直站在反對 DRM 的立場,這次 W3C 通過並公開 DRM 框架規格後,EFF 決定退出 W3C:「World Wide Web Consortium abandons consensus, standardizes DRM with 58.4% support, EFF resigns」。

不算太意外... EFF 對 DRM 的立場一直都很清楚,非常的清楚...