streaming audio – Page 3 – Engineering Radio

Comparison: Over the air listening on FM vs. streaming audio on Android phone

I have had my HTC Android phone for just about a year now, which is enough time to learn the device’s strengths and weaknesses. I have done a fair amount of listening to audio, watching youtube videos and playing .mp3’s to give me some idea of the technical quality and operational issues. Like anything else, these are general observations. Some radio station’s streams sound better than other due to the effort those stations put into audio quality.

The listening test was done with a set of Sony earbuds, which sound far better than the small speaker built into the phone. For ease in streaming audio, I used the TuneIn Radio application for Android by TuneIn Inc. For this test, I only listened to FM broadcast stations, both streaming and over the air.

The over the air tuner is the stock factory radio in my 1997 Jeep Cherokee. I would rate the radio average in every way. The actual tests were done driving around on interstate highways and other major roadways. There were a few instances where I had to give up on the Android phone due to traffic and driving considerations.

My Android phone has an FM tuner installed in it, however, it is really useless. I get only local stations, and then their audio is all hissy and for the most part unlistenable. The HTC FM tuner uses the headphone wire for an antenna, which may be a part of the problem.

Here is a chart of my observations:

Category evaluated	Analog FM radio	Streaming via Android
Overall Station Selection	Only those stations that can be received	Any station that is listed in TuneIn Radio App*
Varity of interesting programming	Only those receivable signals which limits it to a few well programmed stations, the rest being garbage	Almost unlimited, world wide*
Available formats	Only those stations that can be received	Any station that is listed in TuneIn Radio App*
Ease of use	Can press the preset or scan buttons on radio without taking eyes off the road*	Requires squinting at a small screen and pressing several little boxes to get to the desired station
Annoying commercial avoidance	See above on preset and scan buttons*	Very difficult to change stations quickly
Quality of sound	Good to excellent, depending on the station’s signal strength*	Fair to good, depending on the bit rate and network congestion, some stations sound very good and some can sound very bad
Drop outs	Occasional picket fencing with distant stations, otherwise, non-existent*	Varies depending on location, can be quite annoying, especially in mobile environment. App also occasionally locks up and needs to be restarted
Expense	Free, radio came with the vehicle, no paid data service needed*	Requires data plan with smart phone, some plans cap data amounts, can be fairly expensive
Overall enjoyment	Good	Good

*Wins category.

I am having a difficult time assigning the overall enjoyment as well as an over all winner. One the one hand, it was very cool, driving down I-84 in Danbury, CT listening to Howlin’ Wolf on New Orleans’ non-commercial Jazz station, WWOZ. On the other hand, it was a right pain in the ass to get to that point, in rush hour traffic. By the way WWOZ’s web stream is excellent, audio wise.

From a safety and ease of use, the FM radio in the Jeep wins hands down, I just don’t know how many more times I can listen to the same Led Zeppelin song on i95 (that used to be I-95, frankly I thought Steve Jobs copyrighted the lower case i).

The drop outs were also a concern, mostly taking place in on the section of I-84 going through Putnam County, NY. I don’t know if my cell carrier needs to beef up it’s data coverage in that area, or if there were just a great many users on the network checking their e-mail, etc.

If they could sort out the ease of operation problem and get rid of the drop outs, streaming audio over HTC Android would win hands down.

Sound Cards for Broadcast Use

Computer audio sound cards are the norm at nearly all radio stations. I often wonder, am I using the best audio quality sound card? There are some trade offs on the quality vs. cost curve. At the expensive end of the curve, one can spend a lot of money for an excellent sound card. The question is, is it worth it? The laws of diminishing returns states: No. High quality reproduction audio can be obtained for a reasonable price. The one possible exception to that rule would be production studios, especially where music mix downs occur.

I would establish the basic requirement for a professional sound card is balanced audio in and out, either analog, digital or preferably, both. Almost all sound cards work on PCI buss architecture, some are available with PCMCIA (laptop) or USB. For permanent installations, an internal PCI buss card is preferred.

Keeping an apples:apples comparison, this comparison it limited to PCI buss, stereo input/output, analog and digital balanced audio units for general use. Manufactures of these cards often have other units with a higher number of input/output combinations if that is desired. There are several cards to choose from:

The first and preferred general all around sound card that I use is the Digigram VX222HR series. This is a mid price range PCI card, running about $525.00 per copy.

Digigram VX222HR professional sound card

These are the cards preferred by BE Audiovault, ENCO and others. I have found them to be easy to install with copious documentation and driver downloads available on line. The VX series cards are available in 2, 4, 8, or 12 input/output configurations. The HR suffix stands for “High Resolution,” which indicates 192 KHz sample rate. This card is capable of generating baseband composite audio, including RDS and subcarriers, with a program like Breakaway Broadcast.

Quick Specs:

2/2 balanced analog and digital AES/EBU I/Os
Comprehensive set of drivers: driver for the Digigram SDK, as well as low-latency WDM DirectSound, ASIO, and Wave drivers
32-bit/66 MHz PCI Master mode, PCI and PCI-X compatible interface
24-bit/192 kHz converters
LTC input and inter-board Sync
Windows 2003 server, 2008 server, Seven, Eight, Vista, XP (32 and 64 bit), ALSA (Linux)
Hardware SRC on AES input and separate AES sync input (available on special request)

Next is the Lynx L22-PCI. This card comes with a rudimentary 16 channel mixer program. I have found them to be durable and slightly more flexible than the Digigram cards. They run about $670.00 each. Again, capable of 192 KHz sample rate on the analog input/outputs. Like Digigram, Lynx has several other sound cards with multiple input/outputs which are appropriate for broadcast applications.

Specifications:

200kHz sample rate / 100kHz analog bandwidth (Supported with all drivers)
Two 24-bit balanced analog inputs and outputs
+4dBu or -10dBV line levels selectable per channel pair
24-bit AES3 or S/PDIF I/O with full status and subcode support
Sample rate conversion on digital input
Non-audio digital I/O support for Dolby Digital® and HDCD
32-channel / 32-bit digital mixer with 16 sub outputs
Multiple dither algorithms per channel
Word, 256 Word, 13.5MHz or 27MHz clock sync
Extremely low-jitter tunable sample clock generator
Dedicated clock frequency diagnostic hardware
Multiple-board audio data routing and sync
Two LStream™ ports support 8 additional I/O channels each
Compatible with LStream modules for ADAT and AES/EBU standards
Zero-wait state, 16-channel, scatter-gather DMA engine
Windows 2000/XP/XPx64/Seven/Eight/Vista/Vistax64: MME, ASIO 2.0, WDM, DirectSound, Direct Kernel Streaming and GSIF
Macintosh OSX: CoreAudio (10.4)
Linux, FreeBSD: OSS
RoHS Compliant
Optional LStream Expansion Module LS-ADAT: provides sixteen-channel 24-bit ADAT optical I/O (Internal)
Optional LStream Expansion Module LS-AES: provides eight-channel 24-bit/96kHz AES/EBU or S/PDIF digital I/O (Internal)

Audio Science makes several different sound cards, which are used in BSI and others in automation systems. These cards run about $675 each.

Audio Science ASI 5020 professional sound card

Specifications:

6 stereo streams of playback into 2 stereo outputs
4 stereo streams of record from 2 stereo inputs
PCM format with sample rates to 192kHz
Balanced stereo analog I/O with levels to +24dBu
24bit ADC and DAC with 110dB DNR and 0.0015% THD+N
SoundGuard™ transient voltage suppression on all I/O
Short length PCI format (6.6 inches/168mm)
Up to 4 cards in one system
Windows 2000, XP and Linux software drivers available.

There are several other cards and card manufactures which do not use balanced audio. These cards can be used with caution, but it is not recommended in high RF environments like transmitter sites or studios located at transmitter sites. Appropriate measures for converting audio from balanced to unbalanced must be observed.

Further, there are many ethersound systems coming into the product pipeline which convert audio directly to TCP/IP for routing over an ethernet 802.x based network. These systems are coming down in price and are being looked at more favorably by broadcast groups. This is the future of broadcast audio.

Breakaway Broadcast

I am a strong proponent of non-computer based air chain processors. Something about listening to dead air while the computer reboots is annoying and every computer needs to be rebooted every now and again.

All of that being said, I recently had a chance to play around with Breakaway Broadcast audio processing software. I have to say, as a low cost, very versatile platform, it can not be beat. I would put it up against any of the high end FM audio processing, provided one uses a high quality sound card with an adequate sample rate.

Claesson Edwards Audio has developed several software based audio processors for a variety of end uses. They make several recommendations for hardware and operating systems, Pentium 4 3.2 GHz or better, dual core preferred. If one is interested in used the sound card to generate composite audio, then any sound card capable of true 192 KHz sample rate will work. They list several that have been successfully tested on their web site.

For approximately $1,200 dollars or so, one could buy a decent computer, the Breakaway Broadcast software and the Airomate RDS generator software. For a Mom and Pop, LP or community radio station that is looking to do some high end audio processing and or RDS, that is a good deal. I would add a UPS to the computer and keep back up copies of the software installed on an emergency computer just in case. One can never be too safe when it comes to computers, viruses, hackers and other malicious persons.

Things that I like

Inexpensive, the fully licensed version is $200.00. The demo version is free but there is a 30 second promo every thirty minutes.
There are several factory presets, but everything is fully configurable, changes can be named and saved allowing some experimentation.
Audio cards with 192 KHz sample rate or greater can be used to generate composite audio, eliminating the need for a separate stereo generator
RDS capable with additional software (Airomate2, approximate cost $35.00)
The same processing computer can be used for streaming audio and or AM audio processing simultaneously.
Full set of audio calibration tools for AM and FM transmitters, allows correction for tilt, overshoot and linerity. Can add pre-emphasis at any user selectable rate.
Fully adjustable phase rotators.

Things that I don’t generally like:

Computer based system using Windoze operating system

WXPK in White Plains, NY has been using this software to process their streaming audio for about 2 years now. The software itself is extremely stable running on a stand alone Windows box with XP service pack 2.

How expensive is online radio these days?

I read a very good and interesting post on James Critland’s blog. He is somewhat concerned about the trend for mobile wireless providers to no longer offer unlimited data service for a flat fee. I find it interesting that all of these companies seemed to have reached the same conclusions at the same time. But anyway…

The general surmise of James’ post is that the average person will not be able to afford online radio through a 3 or 4G device because of the limited minutes available and the additional charges incurred. (35 quid is about $50.00) To make that meaningful to a US audience, I decided to redo some of James’ math.

Iphones are primarily serviced through ATT. ATT has two different data plans that are coupled with voice plans in a bundle. For example, a 450 minute voice plan and a 200 Mb data plan will cost $55.00. At 900 minute voice plan with a 2 Gb data plan will run $85.00.

Here are a few interesting tid bits and some good math:

A 64 kbps stream runs 7.68 kb per second, or 460 kb per minute (1 kilo bit per second = 0.12 kilo bytes)
1 hour of online listening equals 27,640 k bytes of data transfered
The 200 Mb plan cost $15.00 with voice plan, the 2 Gb plan cost $25.00 with voice plan
The 200 Mb plan would allow for 7 hours of listen time if no other data use occurred
The 2 Gb plan would allow for 72 hours of listen time if no other data use occurred
Beyond those data transfer amounts, extra charges are incurred

Almost 50% of the time spent listening to all radio source (terrestrial, satellite, online) is in the car. The average person in the US listens to radio about 3 hours per day, or 90 hours per month. Half of that time would be 45 hours or so.

Clearly, anyone who is more than a casual listener of online radio will need the 2 Gb plan. However, given the paucity of entertainment available from traditional radio sources, this is not an outlandish amount to pay. I remember in the 70’s when folks were saying cable TV would never catch on.