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June 23, 2005 - Podcast #13 Our email address is hdtvpodcast@mac.com This weeks show Today we will cover the news, explain compression, and talk about integrating an iPod into your home theater. Listener Carlo from Geelong, Australia has provided some good sites for Australian listeners http://www.widescreentv.com.au/ and Digital Broadcasting Australia http://www.dba.org.au/ are some good resources for our Australian listeners.
Compression basics
Lossless compression. Compression that doesn't sacrifice any video or audio quality, no data is lost. Very high quality playback, but not great space savings. Video files are still very large. Some popular lossless codecs are HuffYUV, Lossless MJPEG, and Alparysoft. Lossy compression. Just like it sounds, lossy compression "loses" some of the original audio and video information. That loss of information is what causes video streams to occasionally look blocky or pixelated. The major benefit of lossy compression is that it reduces video file sizes dramatically. Some popular lossy codecs are MPEG1, MPEG2, MPEG4. Intra-frame vs Inter-frame. Some compression algorithms, such as Motion JPEG (MJPEG) compress each frame individually. This is called intra-frame compression because it only relies on the information within each frame for compression. More advanced compression, such as the MPEG family of codecs rely on the changes in information between frames, counting on the fact that most frames will have something in common with the one right before and right after it. This is called inter-frame compression. In inter-frame compression there will be keyframes spaced throughout the sequence of compressed frames. Keyframes are frames that are compressed like an intra-frame codec, so they don't rely on surrounding frames for decompression. The more keyframes that are included in a video stream, the higher the playback quality tends to be, but they also increase file size significantly. MPEG1. The classic video compression algorithm created by the Moving Picture Experts Group in 1992. It was the compression algorithm used for Video Disc and Video CDs. It uses a sequence of keyframes called I-frames interspersed with predictive frames (P-frames) and bi-directional frames (B-frames). I-frames can stand alone, P-frames rely on internal information and information from the most recent P or I-frame. B-frames are what really shrink file size, they rely on both past and future frames. A typical repeating GOP, or Group of Pictures, may be IBBPBBPBB. MPEG1 standard video size is 352 x 240. Check the MPEG1 site for a detailed description of the codec. MPEG2. The video compression algorithm used on DVDs and for ATSC broadcasts, MPEG2 was created by the Moving Picture Experts Group in 1994. The biggest difference between MPEG1 and MPEG2 is that MPEG2 supports interlaced video images, while MPEG1 only supports full frames (progressive). It relies on similar Frame and Group of Picture constructs to compress the video stream, but supports a higher resolutions and bitrates for higher quality video presentations. MPEG2 is also the compression algorithm used internally by many consumer digital video devices, such as DVRs. Check the MPEG2 site for a detailed description of the codec. MPEG4. A fairly new video compression algorithm created by the Moving Picture Experts Group, the first versions of MPEG4 were approved in 1998/99, but subsequent versions are in progress. With the onset of HDTV, video compression again came to the forefront. Originally, MPEG2 was slated to be the codec used for all ATSC broadcasts, including HDTV, but file sizes were just way too big. The major problem is that the bandwidth of a satellite system cannot be increased without launching more satellites. One transponder can typically handle between 6 and 16 standard definition MPEG2 channels or only 1 to 2 HDTV MPEG2 channels. So changing over to HDTV would mean either sacrificing channel availability or significant sacrifices to picture quality. But the new MPEG4 algorithm can stream the same high quality HDTV video in about the same bandwidth as a standard definition MPEG2 stream. This means that when the satellite operators upgrade their channels to HDTV, they don't have to cut back on the number of channels they offer or launch new satellites. Check the MPEG4 site for a detailed description of the codec. iPod and your Home Theater Many of you listen to the HDTV and Home Theater Podcast via your iPods. So this week we like to talk about how you can integrate your iPod into your home theater. The solutions range from simple to elaborate. The real benefit of connecting your iPod to your home theater is that no matter what your musical mood is you will always have something to listen to at your fingertips. Simple You need a Y adapter cable with a mini-plug on one end and red and white RCA connections on the other end. Plug the mini-plug into the headphone connection on the iPod then connect red and white RCA connections into your stereo equipment. Set your stereo receiver to the input that you plugged the iPod into and hit play on your iPod and your done. Obviously this method works for all mp3 players and even laptops. Although this is simple to do you your can't really select your music remotely and the player's battery will eventually run out. Cost:
Slightly less simple Start with simple setup and add a remote and a dock. There are a number of companies manufacturing remotes for the iPod. They all operate on the same basic principal of plugging a receiver into the remote port of the iPod and using a traditional remote to control your iPod. You won't get the LCD info on the remote so unless you know your play lists very well you will be using it to control your music blindly. You can also teach your universal remote to control the iPod at this point. The final addition to this set up is to add a dock to keep it powered. For remotes we recommend the TEN Technology naviPro EX The only issue is that it is an IR remote so it won't go through walls. If you want roam around other rooms in your house and still control your music you'll need a RF remote and Griffin AirClick Wireless RF Remote Buying the AirClick and the naviPro from this link supports the show Cost:
Total $43 to $92 depending on the your preferences. Elaborate
The installation may be a little difficult for some so unless you are handy you may want to leave the install to a professional. If you have an audio only setup you can mount the docking station up to 1000 feet from the equipment. The number goes to 100 feet if you plan on using it for video. You can control the iPod manually or buy one of the remotes we talked about above. In fact Sonnace recommends the NaviPro EX from above. Cost:
Total $640+ So what ever your price range there is a solution. For most of you the middle solution will do the trick. I no longer use CDs. All my music has been ripped, or bought from the iTunes Music Store, and is loaded on my iPod. When we entertain my wife creates a playlist for the evening and we set the iPod up to randomly select songs. We have a large library and can usually go an entire evening without hearing the same song twice. The iPod and our home theater has really changed how we listen to our music. But wait, there is a solution that uses a computer and wireless network for much of the same thing. Apple sells the Airport Express which can wirelessly send your music from your iTunes application running on your computer to the Airport Express. Keyspan sells the Express Remote for $60 that also plugs into the Airport Express that will control the iTunes software from the comfort of your couch. An added plus for using the Airport Express is that it can act as a print server and range extender for your 802.11G wireless network.
Both the Airport Express and the Express Remote are available at Amazon.com. |
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