[求助]关于SINGLE PASS模式

crying99

各位大哥：
        小弟首先祝大家元宵节快乐！
        我用xvid作时时的视频采集，所以只用到了single pass,但是在single pass中的cbr设置中的三个选项小弟非常迷惑，请各位大哥指点迷经！！！！非常感谢

dgwxx

汗……1pass的设置我还真不太了解
等我查查资料

crying99

谢谢你!!!我热情的期待

dgwxx

找到倒是找到了……但是下个星期就要考试了，没时间翻译= =||找到一大段英文材料，楼主如果英文好，就自己看，看完之后如果能翻译出来就太好了 如果英文不好……

C7. Single pass 'more' settings explained

These options are used only when encoding with a fixed bitrate. When using a fixed quantizer/quality mode the codec goes into 'imbecile-mode' and just plainly encodes everything using a very simple set of rules. Needless to say fixed quantizer/quality has very limited use for most of us.

-Reaction Delay Factor: When we talk about fixed bitrate, it isn't really fixed. Instead, the bitrate is averaged between a number of frames. Every next frame gets altered by a value that is the average of the last X number of frames. X is determined by the RDF. So, the bigger this value, the slower the codec will react to quick alterations in complexity and vice versa. Quicker alterations do more accurately reflect the complexity of the source, but slower alterations give a less extreme bitrate distribution.
-Averaging period: This setting does something similar to above, but instead it does it with the quantizers. If this value is 100, it takes the average quantizer computed from the last 100 frames, and then assumes that average quantizer for the next frame.
-Smoothing: The codec keeps a record of how much each frame differs in size from the 'average' size. This is called deviation and it recomputed after each frame. This value is used in conjunction with that deviation. It has a small averaging effect on the whole clip, and the bigger this value is, the smaller the influence.

As a whole, the quality gains from these options are minimal. You really don't want to use single pass. Trust me.

crying99

谢谢你的帮助，大虾就是大虾，我的英文还可以，等我翻译好了我们可以把网站上的xvid注释补充的更详细！！谢谢你！！！

crying99

These options are used only when encoding with a fixed bitrate. When using a fixed quantizer/quality mode the codec goes into 'imbecile-mode' and just plainly encodes everything using a very simple set of rules. Needless to say fixed quantizer/quality has very limited use for most of us.

-Reaction Delay Factor: When we talk about fixed bitrate, it isn't really fixed. Instead, the bitrate is averaged between a number of frames. Every next frame gets altered by a value that is the average of the last X number of frames. X is determined by the RDF. So, the bigger this value, the slower the codec will react to quick alterations in complexity and vice versa. Quicker alterations do more accurately reflect the complexity of the source, but slower alterations give a less extreme bitrate distribution.
-Averaging period: This setting does something similar to above, but instead it does it with the quantizers. If this value is 100, it takes the average quantizer computed from the last 100 frames, and then assumes that average quantizer for the next frame.
-Smoothing: The codec keeps a record of how much each frame differs in size from the 'average' size. This is called deviation and it recomputed after each frame. This value is used in conjunction with that deviation. It has a small averaging effect on the whole clip, and the bigger this value is, the smaller the influence.

As a whole, the quality gains from these options are minimal. You really don't want to use single pass. Trust me.


这些选项被用在固定比特率录入码流时。当使用一个固定的量化器/质量参数模式，编码器将进入一种“低智商模式”，只是平坦的使用一个简单规则进行编码。所以说定比特率编码对我们的用处很小。
反应延迟因素——我们所说的定比特率编码实际上并不是恒定的，其实是在一定的范围内的一个平均值。下一帧的大小将取决于上一帧的平均X数，而X又是由反应延迟因素决定的。
所以这个值越大，编码器将对复杂的动作做出较平缓得反应，反之亦然。而平缓的反应则能更加平均的分配比特率。
平均周期——这个设定和上面的很相似，只不过是用量化器参数来代替而已。如果这个值设为100，那么他将平均前100个量化器的值为下帧估算出的量化器参数。
滤波——编码器会保存每一帧与平均值的差值，然后用这个称为“偏离”的数据再次计算数据。“滤波”值“偏离”值将一起用来进行对数据的处理。他的平均修剪效果非常的小，而且他的值越大影响将越小。


小弟第 一次翻译东东出来见人,希望大家指教!!!

gohuvx

谢谢楼主的翻译

crying99

说到底还是你帮了我！！！！很欣赏你的作风。如果不嫌弃交个朋友-----qq13119290

dgwxx

我QQ一般是24小时在线……可惜人一般24小时不看QQ-______-||

感谢一下楼住的翻译顺便表彰一下，加个精。欢迎以后常来参与讨论~

十字架

<!--QuoteBegin-crying99+Mar 7 2005, 11:48 AM--><div class='quotetop'>QUOTE(crying99 &#064; Mar 7 2005, 11:48 AM)</div><div class='quotemain'><!--QuoteEBegin-->These options are used only when encoding with a fixed bitrate. When using a fixed quantizer/quality mode the codec goes into &#39;imbecile-mode&#39; and just plainly encodes everything using a very simple set of rules. Needless to say fixed quantizer/quality has very limited use for most of us.

-Reaction Delay Factor: When we talk about fixed bitrate, it isn&#39;t really fixed. Instead, the bitrate is averaged between a number of frames. Every next frame gets altered by a value that is the average of the last X number of frames. X is determined by the RDF. So, the bigger this value, the slower the codec will react to quick alterations in complexity and vice versa. Quicker alterations do more accurately reflect the complexity of the source, but slower alterations give a less extreme bitrate distribution.
-Averaging period: This setting does something similar to above, but instead it does it with the quantizers. If this value is 100, it takes the average quantizer computed from the last 100 frames, and then assumes that average quantizer for the next frame.
-Smoothing: The codec keeps a record of how much each frame differs in size from the &#39;average&#39; size. This is called deviation and it recomputed after each frame. This value is used in conjunction with that deviation. It has a small averaging effect on the whole clip, and the bigger this value is, the smaller the influence.

As a whole, the quality gains from these options are minimal. You really don&#39;t want to use single pass. Trust me.
这些选项被用在固定比特率录入码流时。当使用一个固定的量化器/质量参数模式，编码器将进入一种“低智商模式”，只是平坦的使用一个简单规则进行编码。所以说定比特率编码对我们的用处很小。
反应延迟因素——我们所说的定比特率编码实际上并不是恒定的，其实是在一定的范围内的一个平均值。下一帧的大小将取决于上一帧的平均X数，而X又是由反应延迟因素决定的。
所以这个值越大，编码器将对复杂的动作做出较平缓得反应，反之亦然。而平缓的反应则能更加平均的分配比特率。
平均周期——这个设定和上面的很相似，只不过是用量化器参数来代替而已。如果这个值设为100，那么他将平均前100个量化器的值为下帧估算出的量化器参数。
滤波——编码器会保存每一帧与平均值的差值，然后用这个称为“偏离”的数据再次计算数据。“滤波”值“偏离”值将一起用来进行对数据的处理。他的平均修剪效果非常的小，而且他的值越大影响将越小。
小弟第 一次翻译东东出来见人,希望大家指教&#33;&#33;&#33;
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更正小小的错误：
“反应延迟因素——我们所说的定比特率编码实际上并不是恒定的，其实是在一定的范围内的一个平均值。下一帧的大小将取决于上一帧的平均X数，而X又是由反应延迟因素决定的。” 应该是下一帧的大小取决于上X帧的平均数。这里这个X值越小，那么对于encoded的结果会更精确地表现source，但是X值越大，那么可以得到更平均的分配。
“他的平均修剪效果非常的小”应该是它对整片的影响很小。

crying99

谢谢上面的帮助&#33;&#33;&#33;&#33;也谢谢斑竹的鼓励,我会继续努力的.

crying99

对了,我最近正在整理关与xvid应用于时时视频采集的文章,马上就要和大家见面了&#33;&#33;&#33;希望对大家有帮助

dgwxx

呵呵……谢谢搂主~
不过我一般都不会用实时采集XviD，我一般都是先采集MPEG2，然后再压的。麻烦是麻烦，但是效果比实时采集的要好一些。

crying99

谢谢指正

crying99

那样不是要求系统的性能很高，延时也很大，不能满足时时视频的要求？？？？？？请大虾明示

dgwxx

那要看你采集的要求了~
比如，我的电脑是P4 2.4B 512M DDR333，我要实时采集XviD 320*240@25fps的图像，很容易做到，而且效果流畅~但是要采集XviD 640*480@25fps的图像，就根本不达到流畅的标准，或许前几秒还能够跟得上，但时几秒钟以后就会不断地丢帧。
但是实时采集720*540（PAL）的MPEG2编码的图像却能够做到（但是不能同时干消耗系统资源的事情，否则还是会丢帧）。