標籤: 專利

DivX 有哪些專利呢? 到 USPTO 找了一下, 一共有 14 篇, 其中有兩篇是延伸自他們先前的專利.

雖然大家對於 DivX 的認知是一個 video format, 或是一個有 DRM 保護的片商. 但是它主要的專利在於檔案格式, DRM, 以及 de-blocking. 真正和 video 播放有關的專利, 倒是付之闕如. 最有趣的是, 在專利  7,519,274 當中, 它以具體實施例偷渡了這麼幾段話:

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS 

In accordance with the present invention, the version of the video codec used in AVI files is signaled by the FourCC code in the fccHandler field or member of the AVISTREAMHEADER of the corresponding stream header `strh` chunks, and the FourCC code bicompression field or member in the BITMAPINFOHEADER of the corresponding `strf` chunks. 

By way of example, for videos encoded according to a codec developed by DivX Networks, Inc., 10350 Science Center Drive, Building 14, Suite 140, San Diego, Calif. 92121, the FourCC codes fccHandler in the stream header (`strh`) of the AVISTREAMHEADER is set to "divx" or "DIVX". Furthermore, the FourCC (DWORD) code biCompression in the BITMAPINFOHEADER of the corresponding `strf` chunks is set to signify the detailed codec version. 

Specifically by way of example, for version DivX 3.11, `div3` or `div4` is used in AVISTREAMHEADER, and `div3` or `div4` is used in BITMAPINFOHEADER; for version DivX 4.x, `divx` is used in AVISTREAMHEADER, and `divx` is used in BITMAPINFOHEADER; and for version DivX 5.x, `divx` is used in AVISTREAMHEADER, and `dx50` is used in BITMAPINFOHEADER. 

By now it should be appreciated that a file format for storing digital data with a high compression rate has been described. A file format in accordance with the present invention is compatible with high level data compressing algorithms, such as MPEG-4. Its data compression ratio is about six to ten times higher than a standard DVD format. In accordance with the present invention, the file format is capable of storing data in multiple streams or tracks. The file format is also able to encode and archive video, audio, and text data on easily accessible streams or tracks. Furthermore, the file format is able to provide protection of the copyright of the digitized content. 

While the invention is susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof have been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention. The present invention is limited only by the claims that follow. 

儘管 DivX 努力在不具備專利效力的章節裡面幫自己打廣告, 重申 DivX encoder 的優點,還是難掩它沒有主流 encoder 專利的缺憾.畢竟 encoder 做得再好, 還是要和 decoder 相容. 就以 7,519,274 這個專利來說,它只能在檔案格式上做文章.雖然專利名稱有 multi track, 但申請專利的人並沒有忘記把一個 track 的狀況包括進去.以他們的第一條 claim 來說.

1. A playback device configured to play data encoded in a multimedia file, comprising: a processor configured to read the multimedia file; wherein the multimedia file has at least one video track and includes a video stream descriptor list comprising: a video stream header chunk; a video stream format chunk following said video stream header chunk; and a video stream name chunk including a string indicating a video stream in said at least one video track; said video stream descriptor list further comprising a video stream header data chunk in response to said at least one video track being a digital rights management (DRM) protected video, said video stream header data chunk following said video stream format chunk in said video stream descriptor list; said video stream header data chunk in said video stream descriptor list including a DRM information data block comprising: a first member specifying a version of the DRM; and a second member specifying a protection of the DRM said DRM information data block in said video stream header data chunk having a data structure defined as: TABLE-US-00020 typedef _DRMinfo { WORD wVersion; STR sDRMinfo; } DRMINFO. 

看了雖然很眼花, 但簡單講就是: 多媒體檔案在 video stream descriptor 裡面有至少一個 video track, track 裡面有 video stream descriptor. 其中又有 video stream header chunk, format chunk, name chunk, data chunk, format chunk. 在 data chunk 裡面有 DRM revision 和 DRM information data chunk.

以我的認知是, 如果只有一個 track, 而且不受 DRM 保護, 就不受這一條的限制 – 因為那樣把所有傳統的檔案都包括進去了.為了防堵那些不用 track 為單位的檔案, 本專利在 claim 42 強調包含 multiple chapter. 而 claim 43 涵蓋只有一個 chapter, 但是有多個 data chunk 的狀況. claim 45 規範有 subtitle 檔案, claim 46 則規範有 subtitle, 但分成多個 data chunk 的狀況. claim 48 又把前述的 subtile 狀況, 加上有 DRM 時的例子…, 目標很顯然就是想一網打盡, 能想的都想了…從這個角度來看, 還真是滿厲害的.