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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


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。

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.


Firefox 51 (現在是 48) 將會支援 FLAC

Hacker News Daily 上看到 Firefox 要支援無損格式 FLAC 的消息:「Bug 1195723 - FLAC support / Create FLAC MediaDataDemuxer」。

隔壁棚關於 Google Chrome 也有 FLAC 相關的「Support FLAC audio codec」,也是等很久都沒消息,不知道會不會因為 Firefox 有進度後...

現在如果要無損的話只有 WAV 可以用 (話雖如此,IE 還是要到 Edge 才有支援),改用 FLAC 大約可以省下 40% 的大小 (平均值,依照音樂的類型會有不一樣的壓縮率),如果普及的話,不知道 YouTube 之類的服務在轉播音樂會時會不會試著拼看看?

Cisco 開發新的 Video Codec:Thor

Cisco 開發新的 Video Codec 與 HEVC (H.265) 競爭,專案名稱叫做 Thor:「World, Meet Thor – a Project to Hammer Out a Royalty Free Video Codec」。


Unfortunately, the patent licensing situation for H.265 has recently taken a turn for the worse. Two distinct patent licensing pools have formed so far, and many license holders are not represented in either. There is just one license pool for H.264. The total costs to license H.265 from these two pools is up to sixteen times more expensive than H.264, per unit. H.264 had an upper bound on yearly licensing costs, whereas H.265 has no such upper limit.

不過一開頭寫到 VP9 是 proprietary 的描述讓人很不解:

There are two of note – Google’s proprietary VP9 codec, and the industry standard H.265 (HEVC) codec, which is the successor to H.264 (AVC).

往下拉 comment 看果然就有人提出來:

How exactly is VP9 more "proprietary" than Thor? Both are open sourced under BSD license, both are royalty free, both are intended to be unencumbered by patents. Are you defining "proprietary" as "not controlled by Cisco"?


Opus 1.1 釋出...

Opus 是個 royalty-free 的 audio codec,據官方說法是個多用途的 codec (而且表現都很好):

前幾天 Opus 終於釋出 1.1 版 (1.0 版已經是一年前的事情):「Opus 1.1 Released」。

這個版本在 ARM 上的效能大幅提昇 (包括了壓縮與解壓縮),很明顯是針對行動裝置的改善:「[opus] Opus 1.1 released」。

不過好像都沒看到 bitrate 夠高時的比較...

Cisco 的 H.264 實作放出來了...

Cisco 在十月宣佈的 Open source H.264 codec 已經在 GitHub 上放出來了:「Open Source H.264 Codec」,這個實作包括了 encoder 與 decoder。

用的是 BSD 2-Clause License:「LICENSE」。

目前的支援度:(直接複製 OS Support 這段)

  • Windows 64-bit and 32-bit (initial release is only 32-bit, 64-bit will follow soon)
  • Mac OS X 64-bit (initial release does not include this target, will follow soon)
  • Linux 64-bit and 32-bit (initial release is only 32-bit, 64-bit will follow soon)
  • Android 32-bit (initial release does not include this target, will follow soon)
  • iOS 64-bit and 32-bit (not supported yet, may be added in the future)

看起來目前只支援桌機上的 32bits...

然後已知的問題:(複製 Known Issues 這段)

  • Encoder errors when resolution exceeds 3840x2160
  • Encoder errors when compressed frame size exceeds half uncompressed size
  • Encoder console app only support multiple of 16 width/height for now
  • Decoder errors when compressed frame size exceeds 1MB


VP8 將可以無償使用 MPEG LA 重要的專利...

Slashdot 上看到 VP8 可以使用 MPEG LA「重要的」專利:「Google and MPEG LA Reach VP8 Patent Agreement」,這次授權不僅限於 Google,還包括讓 Google 可以免費授權其他人使用。

官方公告包括了 WebM 網站上「VP8 and MPEG LA」,MPEG LA 的「Google and MPEG LA Announce Agreement Covering VP8 Video Format」... (話說 MPEG LA 的聯絡窗口叫做 Tom O'Reilly,跟那位有關嗎?:p)

TechCrunch 也給了一篇分析「Google And MPEG LA Sign Licensing Agreement Covering Google’s VP8 Video Codec, Clearing The Way For Wider Adoption」。