引用:
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作者hidexebih
另外請問有沒有哪些軟體是專拿來跑這樣的overlay輸出的呢?  |
以下引自
Hardware Overlay Wikipedia....
引用:
The way a computer draws on its display is by writing a bitmapped representation of the graphics into a special portion of its memory known as video memory. Without any hardware overlays, there is only one chunk of video memory which all applications must share - and the location of a given application's video memory moves whenever the user changes the position of the application's window. With shared video memory, an application must constantly check that it is only writing to memory that belongs to that application.
When running a high-bandwidth video application such as a game or a movie player, the computing power and complexity needed to perform this constant clipping and checking negatively impacts performance and compatibility. To escape these limitations, the hardware overlay was invented. In addition, the GPU provides an efficient way to scale the video in size and often performs color format conversions (e.g. MPEG-2's YCbCr into RGB).
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以純粹只看不錄而言,只要I/O跑得動(i.e. BUS頻寬夠,而且VGA的Overlay engine夠力
),HOST CPU須要做的其實只是把系統initialize起來和UI而已,那就是鵝前面說吃不了多少CPU的原因
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引用:
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作者hidexebih
我有個粗糙的想法
以Osprey440來說，composite input擷取的解析度最多也就720x480...
如果合成這種解析度的四個畫面，那就是1440*960
我在想這樣的畫面透過顯示卡送到Full HD的LCD上面時，應該不至於劣化的很嚴重吧?
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其實這還是得看您打算在這台"6分割"上秀啥,如果是一般SD等級的視訊(i.e.圖形為主,低解析度的文字為輔),那一般PC的Composite/S端子可能還算堪用吧,比如說CX2388x的datasheet上寫著....
引用:
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The video stream consumes bus bandwidth with average data rates varying from 44MBps for full-size 768 × 576 PAL RGB32, to 4.6MBps for NTSC CIF 320 × 240 RGB16, to 0.14 MBps for NTSC ICON 80 × 60 8-bit mode.
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由以上解析度對頻寬的預估可以知道為啥Osprey-440要做成PCI-X了(BTW,Decklink HDMI截取卡其實也都是PCI-E x1的,可見以1080i為例HDMI的產出值也不會超出PCI-E x1的250MBps
),而對鵝來說純HDMI截取卡只要US$2xx起跳其實已經算非常平價了,只是不知道VGA的Overlay engine經不經得起高解析/大流量的source一起多P就是了
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引用:
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作者hidexebih
當然能吃HD訊源的卡會更有彈性
不過我想這樣的工作站應該也是一筆
話說回來，如果插上四張Decklink HD Extreme做HDMI擷取...
匯流排會不會產生頻寬的問題呢? |
一般PCI-E的chipset通常可以config成16+4*1 / 16+1*3或8+8+4*1 / 8+8+1*3,以此看來若是插4張PCI-E x1的純HDMI截取卡應該不會有太大的問題(只要VGA跑得動,至於M/B穩不穩就再說了
),另外HD Extreme因為是PCI-E x4的,光要找有16+4*4的M/B就有點麻煩了,如果SDI不是很重要的話可能就要取捨一下了
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引用:
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作者hidexebih
我最早也有類似的想法...
不過有點怕會被看的人笑...囧 |
其實術業有專攻,老闆總不能指望每個人都是十項全能吧
....像鵝主要是搞系統的,純就對搞一個6xSD對1xHD的6分割而言,只要UI不是太講究,自然是能不動coding就不動coding了
....BTW,如果是Osprey的卡在linux下要驅動問題應該不大(頂多當成多路的BT878或CX2388x驅動吧
),用linux包一包(就當是用linux兜一個另類的DVR吧
)或許就能唬倒一般人了,至於Decklink的卡因為鵝還沒機會玩過,鵝就不敢亂說了,但至少應該會有M$ Win的driver可用吧
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