DVB-H -- THE OTHER OFF-AIR DTV
Hello there -- I know it has been a really long time since I've posted something new, but with me busy testing and evaluating products, I really haven't had a chance to find something new to post. However, now that CES is over I can provide even more extensive information on DTV over mobile phones, or DVB-H. In the months to come, you will be hearing about Modeo (1.6 GHz L-Band developed by Houston/UK-based Crown Castle) and MediaFLO (700 MHz UHF band developed by San Diego based Qualcomm). These are new terrestrial broadcasts of multiple channels of live and recorded video and audio to be played on portable mobile devices, like mobile phones, PDAs, laptops, and portable media devices, like the iPod.
From an antenna standpoint, receiving this programming would require antennas the size of mobile phones. Because of the frequencies alcated for these services, the antennas, and in turn the devices, would easily be portable, especially since the antenna size would be small out of necessity, as opposed to a 9-foot wide dipole to effectively receive VHF channel 2. Also because the signals are digital, I can confidently say that receiving these DVB-H services have similarities to receiving off-air broadcast DTV/HDTV. The differences would be the modulation and required bitrate, which is the job of the receiver circuitry.
The Modeo service (www.modeo.com) plans to use the Windows Media codec and stream video at 320 x 240 4:3 resolution at 30 frames per second (fps), the same resolution as the Apple video iPod. I think the advantage of using Windows Media is that the opportunity arises for PC cards and antennas to receive the Modeo service on PCs and laptops, and record them like a PVR. Then the content, likely protected to prevent redistribution to non-subscribers, could be replayed easily on the PC, especially in Microsoft Media Center. It might be possible even to watch this recorded programming in other rooms using devices with Media Center Extenders. I have watched 320 x 240 videos on my Media Center PC on a 480i analog 25" set, and yes while the resolution may look cheap compared to broadcast DTV, I would have to say it looks no worse than a VHS video that taped an analog NTSC program.
The number of channels that can be provided is dependent on the selected resoltution, and the amount of allocated bandwidth. The higher the resolution, the more bitrate is needed. It is like downconverting an HDTV program into DVD, you would the video file size since the required bitrate would be lower, but you give up resolution. For an 8-VSB ATSC broadcast DTV signal, a broadcaster would be restricted to 6 480i standard-definition DTV channels, with 2-3 Mbps bitrateper channel encoded into 19.5 Mbps of bandwidth (at least 1.5-2 Mbps are needed for PSIP tables). For 320 x 240 resolution at 30 fps, a bitrate of only 640 kpbs is required. In case you're wondering how I know this, I just bought a handheld digital camera with QuickTime video clip recording, and I got this information off the manual specifications; it is capable of 640 x 480 (480i) recording at 30 fps as well as QVGA (320 x 240) recording. My camera stores the clips on Secure Digital media cards, so if I am willing to give up resolution, I can get more recording time. I have a 1 GB SD card allowing me to get an hour of 640 x 480 recording at a 2 Mbps bitrate, with an option of recording less at 3 Mbps for video where there may be a lot of fast movement, like a car race. Incidentally, the camera I have is a Sanyo VPC-C5, and they will be releasing a 720p HD handheld camera ($800 retail, and you'd better be willing to shell out $150-$200 more for a 2 GB SD card since you would be encoding at 8-10 Mbps) in April.
Back to Modeo, with QVGA resolution, which would look good on handheld devices like video iPods, and 12 MHz badwidth, up to 30 channels, maybe more, can be provided by this service. In addition, radio programs and podcasts may be offered by this service. This would be a lot more content than a maximum 12 480i channels on 2 DTV off-air channels, and fewer to provide HDTV. For MediaFLO (www.qualcomm.com/mediaflo/index.shtml), I believe they plan to use the QuickTime video codec, or a similar global standard, especially since Qualcomm has its proprietary audio codec, QCP (Qualcomm Pure Voice), which is played primarily on PCs using QuickTime. I know this because I have a Palm Treo smartphone using QCP audio, I recorded my voice, emailed it to my PC using SMS through my wireless provider, and found I needed QuickTime to play my recorded clip.
Just like off-air HDTV reception, in order to get a consistently solid stream on a device, these would have to be a minimal bit error rate (BER) in the signal collected by the antenna and being demodulated by the receiver. So, the receivers and chipsets for DVB-H would have to be capable of correcting in areas of high-multipath, since the devices themselves would likely use an omidirectional antenna. The problem with omnidirectional antennas is that they can collect desired and undesired interference signals from any direction. A directional antenna, however, can reject multipath, and deliver signals to the receiver with a lower bit bit error rate. When the signal has a lower bit error rate, the bitrate is maximized, the receiver has an easier time decoding the signal, and the video streams are consistently smooth.
Crown Castle decided to use an unlicensed US L-band that was available for purchase, because they feel that in this frequency assignment there would be less interference from other sources. This would give the devices a better chance to consistently decode signals even with omnidirectional antennas. Meanwhile, MediaFLO needs to contend with existing broadcast TV signals now, and public safety networks in the future after broadcast channels 52-69 are returned when analog broadcasting ends. So Modeo has the edge there, it now comes down to the content deals that will be going down in the next few months to see which service will have the edge. You can expect Modeo to launch its service on a trial basis in New York later this year, in Pittsburgh now, and in 30 markets in 2007. MediaFLO will be rolling out about the same time. Whatever the case, market research indicates DVB-H to become a billion-dollar industry by 2009. So get ready, within a year ot two, you'll probably be keeping an eye on the big game while attending your kids' soccer game, or checking out the morning news on the train to work.
For more information on DVB-H, visit the Mobile DTV Alliance Web site.
Hello there -- I know it has been a really long time since I've posted something new, but with me busy testing and evaluating products, I really haven't had a chance to find something new to post. However, now that CES is over I can provide even more extensive information on DTV over mobile phones, or DVB-H. In the months to come, you will be hearing about Modeo (1.6 GHz L-Band developed by Houston/UK-based Crown Castle) and MediaFLO (700 MHz UHF band developed by San Diego based Qualcomm). These are new terrestrial broadcasts of multiple channels of live and recorded video and audio to be played on portable mobile devices, like mobile phones, PDAs, laptops, and portable media devices, like the iPod.
From an antenna standpoint, receiving this programming would require antennas the size of mobile phones. Because of the frequencies alcated for these services, the antennas, and in turn the devices, would easily be portable, especially since the antenna size would be small out of necessity, as opposed to a 9-foot wide dipole to effectively receive VHF channel 2. Also because the signals are digital, I can confidently say that receiving these DVB-H services have similarities to receiving off-air broadcast DTV/HDTV. The differences would be the modulation and required bitrate, which is the job of the receiver circuitry.
The Modeo service (www.modeo.com) plans to use the Windows Media codec and stream video at 320 x 240 4:3 resolution at 30 frames per second (fps), the same resolution as the Apple video iPod. I think the advantage of using Windows Media is that the opportunity arises for PC cards and antennas to receive the Modeo service on PCs and laptops, and record them like a PVR. Then the content, likely protected to prevent redistribution to non-subscribers, could be replayed easily on the PC, especially in Microsoft Media Center. It might be possible even to watch this recorded programming in other rooms using devices with Media Center Extenders. I have watched 320 x 240 videos on my Media Center PC on a 480i analog 25" set, and yes while the resolution may look cheap compared to broadcast DTV, I would have to say it looks no worse than a VHS video that taped an analog NTSC program.
The number of channels that can be provided is dependent on the selected resoltution, and the amount of allocated bandwidth. The higher the resolution, the more bitrate is needed. It is like downconverting an HDTV program into DVD, you would the video file size since the required bitrate would be lower, but you give up resolution. For an 8-VSB ATSC broadcast DTV signal, a broadcaster would be restricted to 6 480i standard-definition DTV channels, with 2-3 Mbps bitrateper channel encoded into 19.5 Mbps of bandwidth (at least 1.5-2 Mbps are needed for PSIP tables). For 320 x 240 resolution at 30 fps, a bitrate of only 640 kpbs is required. In case you're wondering how I know this, I just bought a handheld digital camera with QuickTime video clip recording, and I got this information off the manual specifications; it is capable of 640 x 480 (480i) recording at 30 fps as well as QVGA (320 x 240) recording. My camera stores the clips on Secure Digital media cards, so if I am willing to give up resolution, I can get more recording time. I have a 1 GB SD card allowing me to get an hour of 640 x 480 recording at a 2 Mbps bitrate, with an option of recording less at 3 Mbps for video where there may be a lot of fast movement, like a car race. Incidentally, the camera I have is a Sanyo VPC-C5, and they will be releasing a 720p HD handheld camera ($800 retail, and you'd better be willing to shell out $150-$200 more for a 2 GB SD card since you would be encoding at 8-10 Mbps) in April.
Back to Modeo, with QVGA resolution, which would look good on handheld devices like video iPods, and 12 MHz badwidth, up to 30 channels, maybe more, can be provided by this service. In addition, radio programs and podcasts may be offered by this service. This would be a lot more content than a maximum 12 480i channels on 2 DTV off-air channels, and fewer to provide HDTV. For MediaFLO (www.qualcomm.com/mediaflo/index.shtml), I believe they plan to use the QuickTime video codec, or a similar global standard, especially since Qualcomm has its proprietary audio codec, QCP (Qualcomm Pure Voice), which is played primarily on PCs using QuickTime. I know this because I have a Palm Treo smartphone using QCP audio, I recorded my voice, emailed it to my PC using SMS through my wireless provider, and found I needed QuickTime to play my recorded clip.
Just like off-air HDTV reception, in order to get a consistently solid stream on a device, these would have to be a minimal bit error rate (BER) in the signal collected by the antenna and being demodulated by the receiver. So, the receivers and chipsets for DVB-H would have to be capable of correcting in areas of high-multipath, since the devices themselves would likely use an omidirectional antenna. The problem with omnidirectional antennas is that they can collect desired and undesired interference signals from any direction. A directional antenna, however, can reject multipath, and deliver signals to the receiver with a lower bit bit error rate. When the signal has a lower bit error rate, the bitrate is maximized, the receiver has an easier time decoding the signal, and the video streams are consistently smooth.
Crown Castle decided to use an unlicensed US L-band that was available for purchase, because they feel that in this frequency assignment there would be less interference from other sources. This would give the devices a better chance to consistently decode signals even with omnidirectional antennas. Meanwhile, MediaFLO needs to contend with existing broadcast TV signals now, and public safety networks in the future after broadcast channels 52-69 are returned when analog broadcasting ends. So Modeo has the edge there, it now comes down to the content deals that will be going down in the next few months to see which service will have the edge. You can expect Modeo to launch its service on a trial basis in New York later this year, in Pittsburgh now, and in 30 markets in 2007. MediaFLO will be rolling out about the same time. Whatever the case, market research indicates DVB-H to become a billion-dollar industry by 2009. So get ready, within a year ot two, you'll probably be keeping an eye on the big game while attending your kids' soccer game, or checking out the morning news on the train to work.
For more information on DVB-H, visit the Mobile DTV Alliance Web site.
posted by Derek (IA) | 8:39 AM
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