From: Helmut Hlavacs <[EMAIL PROTECTED]> Subject: Re: Optimizing video quality with unique RealProducer settings Hi Yvan! RealForum wrote: > From: "Yvan Gagnon" <[EMAIL PROTECTED]> > Subject: Optimizing video quality with unique RealProducer settings > > I was wondering if anyone here might be willing to share their > recommendations on what the ideal settings are for the encoding of different > bitrate realvideos. I've done quite a bit of research and experimenting, > and I'm somewhat curious about certain things. > > Typically, I encode my realvideo files for 4 different bitrates: 28k, 56k, > dual isdn, & DSL/Cable Modem. While analyzing the statistics of the some of > the videos created by encoding.com (who I've found get some pretty > outstanding results) I noticed that they generally use the following > settings: > > 28k - video : 160x120 - 6 fps | audio 6.5 kbps > 56k - video : 176x132 - 6 fps | audio 8.5 kbps > Dual ISDN - video : 240x180 - 12 fps | audio 8.5 kbps > DSL/Cable Modem - video : 320x240 - 15 fps | audio 16 kbps > > Question #1 : > > If a Dual ISDN line can, in theory, handle something like 112 or 128 kbps, > .. why use a bitrate of only 80 kbps? I'm noticing that this is also the > default setting assigned in RealProducer, and I'm just wondering if this > bitrate, -- and if all of these specific bitrates, -- were chosen for a > specific reason, .. like to allow for overhead (web surfing, email, etc, > ... ) or if there's a performance consideration of some sort. Why not > encode at 100kbps?? Or higher even? I mean, . isn't an ISDN line > dedicated? According to information from the realsystem G2 production guide, section "Choosing a target bandwidth", you only count on 75% of the total bandwidth (2x56kbps*0.75 = 84 kbps). The reason for this is that each packet carries significant overhead like UDP packet header and SureStream Packet header. The 80kbps account on the actual video and audio information data that is sent. Also, other information is likely to be sent over the same connection, though not visible to you. Choosing 100% of the bitrate that can be sent over your connection would not make much sense, as this cannot be kept constant for all of the time. Also, after network congestions, the RealPlayer buffer should be refilled once more, so you might temporarily need a higher bw. > > > Question #2 : > > Obviously, the above settings can't always apply. For example, I had to > encode a clip this afternoon that had lots of fast motion in it, and I > couldn't help but notice that it looked like total shit at the lower > bitrates (28k and 56k) . In these cases, meaning where there is lots of > motion in the video to be encoded, what changes can I make to my settngs to > optimize clarity and at least get some half-decent looking results ?? The > only thing that I've noticed makes a difference is when I change the "Video > Quality" setting to "Sharpest Image Video", .. though the change is barely > even noticeable. I would try to set the fps to 1.5. This makes RealVideo to put more picture information (-> better quality) into each frame. > > > Question #3 : > > What are the actual differences between "Normal Motion Video", "Sharpest > Image Video" and "Smoothest Motion Video" and when is it best to use each ?? I would suppose that Sharpest Image Video chooses a better image quality and reduces the fps. Smoothest Motion Video chooses a higher fps over image quality. Normal Motion Video is somewhere in between. Remember that the bits per second are kept constant, so RealVideo must save bandwidth either in image quality or fps. > > > Question #4 : > > I don't know if I'm just having some kind of technical problem or if there's > a bug in the new realplayer, .. but when I encode a video at 15 fps, and > then monitor the statistics while playing the resulting realvideo file > locally using realplayer, for some reason, the frame rate that it plays back > with is nowhere near what I encoded it at. For example, If I've endcoded a > realvideo file at 15fps, .. why is realplayer telling me that it's playing > back at only 6-7 fps --- locally ?? This is a PIII 500 w/ 256 mb ram we're > talking about here. Might this have anything to do with the fact that the > AVIs I'm encoding were originally captured at 15fps? Or should this not > make any difference? > No idea, sorry. Cheers Helmut ******************************************************* The RealForum is an email discussion group focused on using RealNetworks products. The RealForum is a place to post messages about the best methods for creating content using RealNetworks technologies and the planning and implementation of streaming-media web sites. Archives of RealForum can be found at http://realforum.real.com If you ever want to remove yourself from this mailing list, you can send mail to <[EMAIL PROTECTED]> with the following command in the body of your email message: unsubscribe realforum or from another account, besides the address you subscribed with: unsubscribe realforum <[EMAIL PROTECTED]>
