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Thread: Sonic SD-2000 Encoder

  1. #1
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    Default Sonic SD-2000 Encoder

    Hmm..Sonic have recently brought out a their Sonic SD-2000 Mpeg2 hardware encoder which supports two-pass CBR encoding.

    Wos dat all about den? (i.e. the benefit of multi-passing CBR encoding)
    Lloyd

    That's my opinion. If you don't like it I have others

    System: Apple Macbook Pro 17, and an external Freecom 500GB eSATA drive.
    Software: Final Cut Studio 2 (FCP 6, Motion 3, Soundtrack Pro 2, Color, DVD Studio Pro 4, Compressor 3), Sonicfire Pro 4.5
    Favourite Resources: Findsounds.com, Free DVD menus, Ken Stone's FCP Page, Wikivid

  2. #2
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    Default

    Apparently

    Standard CBR only uses a single encoding pass. You provide your content as input samples, the codec compresses the content and returns output samples. It is also possible to process input samples twice. On the first pass, the codec performs calculations to optimize encoding for your content. On the second pass, the codec uses the data gathered during the first pass to encode the content.

    Two-pass CBR encoding has many advantages. It often yields significant quality gains over standard CBR encoding without changing any of the buffering requirements. This makes this encoding mode ideal for content that is streamed over a network.
    and even more confusingly:

    With CBR encoding, you specify the average bit rate that you want to maintain and then set the size of the buffer. The bit rate will fluctuate across the stream; however, the fluctuations are constrained by the buffer size. The content quality also fluctuates to ensure that the buffer does not overflow or underflow. (If you want to guarantee the quality of the encoded output, use quality based VBR encoding.) The size of the buffer determines the amount of initial delay when the content is played, but using CBR encoding ensures that the content is streamed smoothly, assuming that the bit rate is compatible with the client connection speed. If possible, use two-pass CBR encoding to reach a higher quality without losing the advantages of CBR encoding.
    but I think we're okay now:

    VBR encoding is good for content that is downloaded and played either locally or on a device that has a constrained reading speed, such as a CD or DVD player. Peak VBR encoding is also good for streaming. The advantage of VBR encoding is that it compensates for changes in the complexity of the content (such as switching between slow and fast motion).

    You can use the following VBR modes:

    Quality based VBR (WMENC_PVM_UNCONSTRAINED). You specify a desired quality level (from 0 to 100), then during encoding, the bit rate fluctuates according to the complexity of the stream. A higher bit rate is used for intense detail or high motion, and a lower bit rate is used for simple content. The advantage of quality based VBR encoding is that the quality remains consistent across all streams for which you specify the same quality setting. The disadvantage is that you cannot predict the file size or bandwidth requirements of the encoded content. Quality based VBR encoding uses one-pass encoding. If you are encoding audio content, you can use the Windows Media Audio 9 Lossless codec. Lossless encoding produces superior quality results, while also providing some compression of the data.
    Bit rate-based VBR (WMENC_PVM_BITRATE_BASED). You specify the desired average bit rate. At any point, the bit rate may exceed the average bit rate but the overall bit rate does not exceed the average bit rate. Bit rate-based VBR encoding uses two-pass encoding. In the first pass, the data complexities are analyzed. Then, in the second pass, the quality level is set to achieve the average bit rate. The advantage of bit rate-based VBR encoding is that the compressed stream will achieve the highest-possible quality level while staying within a predictable average bandwidth.
    Peak bit rate-based (VBR WMENC_PVM_PEAK). You specify the desired average bit rate and the peak bit rate. The encoding process determines the image quality that can be achieved without exceeding the peak bit rate. The bit rate does fluctuate during encoding, but does not exceed the specified peak bit rate. Use this option when you plan to distribute the content for playback on a device that has a constrained reading speed, such as a CD or DVD player. Peak bit rate-based VBR encoding uses two-pass encoding, and cannot be output to a live broadcast (only archived to a file).
    The quality based, VBR encoding mode is not recommended for use in a streaming scenario due to the high bit-rate peaks in the content. In a streaming scenario, when all players reach the point in the stream with a high bit rate at approximately the same time, there is a large peak in demand that may exceed the network capacity, resulting in a negative playback experience.
    So in summary:

    Variable bit rate (VBR) encoding is an alternative to constant bit rate encoding and is supported by some codecs. Where CBR encoding strives to maintain the bit rate of the encoded media, VBR strives to achieve the best possible quality of the encoded media.
    http://www.viscomsoft.com/support/

    So that's why two pass CBR exists! It attempts to maintain a constant bitrate which is achieved by analysing in the first pass and encoding in the second. Even though it's a constant bitrate, the video still has to be analysed to be encoded.

  3. #3
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    Default

    Excellent reply Marc. I searched everywhere for an answer to my question but kept drawing blanks. I visited the site you posted a link to but couldn't find where the information you quoted was located. Any chance of a link to the actual page?

    Thanks again, I learnt something new from all that.
    Lloyd

    That's my opinion. If you don't like it I have others

    System: Apple Macbook Pro 17, and an external Freecom 500GB eSATA drive.
    Software: Final Cut Studio 2 (FCP 6, Motion 3, Soundtrack Pro 2, Color, DVD Studio Pro 4, Compressor 3), Sonicfire Pro 4.5
    Favourite Resources: Findsounds.com, Free DVD menus, Ken Stone's FCP Page, Wikivid

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