ATSC Digital Audio Quality, Technology, Issues - Page 5 - Canadian TV, Computing and Home Theatre Forums

stampeder · 2010-10-31, 01:50 PM

There is no technical reason why ATSC would have lower bass levels than NTSC analogue TV. Personally I find the audio via DTV to be superb. There are lots of reasons why a home user would experience different levels. Sometimes it is the fault of the broadcaster, sometimes it is the gear being used by the consumer.

Please give us a detailed list of your home equipment so that we can see if the problem is at your end.

chengbin · 2010-10-31, 01:56 PM

I find DTV's audio to be great as well. There is a (sometimes) very noticeable improvement in sound quality going from analog to DTV.

I have a LG 50PK550 connected to a Logitech Z-5500 via optical. I have a crappy rabbit ear antenna connected to my TV.

stampeder · 2010-10-31, 02:01 PM

If you test with just the LG's speakers with the Logitech system disconnected is there a difference in the bass level between ATSC and NTSC channels?

chengbin · 2010-10-31, 02:03 PM

TV speakers do not produce bass, so I can't tell.

stampeder · 2010-10-31, 02:04 PM

That's not what I'm asking. Can you test with no connection to the Logitech system please?

Does the LG's own audio amplifier give equal levels between ATSC and NTSC channels?

chengbin · 2010-10-31, 02:08 PM

Let me get back to you when it is my turn to watch TV. Currently the TV is occupied.

Are you trying to confirm that ATSC and NTSC's sound level is equal? I don't think so, but I'll verify. I remember increasing my volume when doing that A/B test for OMNI 2 today, and even with the increased volume on the ATSC channel, the NTSC channel has more bass, and it has more bass with a lower "overall" volume.

stampeder · 2010-10-31, 02:10 PM

No problem. Do you connect your TV to your audio system via digital coax, optical, or other?

chengbin · 2010-10-31, 02:13 PM

I have it connected via digital optical.

BTW I've edited my last post with additional information.

Some more information. There was only one time I remember DTV with the right amount of bass, and it was the 2010 Teen Choice Awards. I was expecting bass heavy songs (of course), so I turned my sub volume to the max to compensate for the low bass levels. Later I had to turn it down to normal because it had so much bass it sounded bad.

JamesK · 2010-10-31, 03:39 PM

^^^^
One possibility is that analog sounds like it has more bass, because it has less high end. Analog TV sound is FM with 15 kHz maximum modulating frequency and 25 kHz deviation, compared to FM radio's 75 kHz deviation. This will reduce the levels of high frequency audio. The lower deviation will result in higher noise level and the TV's audio circuits may be tuned to filter out that noise and, in the process, further reduce the top end. I don't recall the details for ATSC audio, but IIRC it's better than CD quality, which can contain frequencies approaching 22 kHz and has a much lower noise level.

chengbin · 2010-10-31, 04:06 PM

@JamesK

I know exactly what you're talking about (I boost treble on my computer speakers), but the difference is large enough that it can't be that.

ATSC does not have better sound quality than CD. ATSC's audio is 6 channel AC3 compressed @ 448Kbps (or 384Kbps?) @ 48KHz. CD is uncompressed @ 1411Kbps for 2 channels @ 44.1KHz. AC3 is technically better being 48KHz, translating into 24KHz of usable frequency spectrum, rather than 22KHz of CD. But CD's *uncompressed* stereo, so it doesn't get better than this for 2 channel sound @ 44.1KHz. Therefore CD is still better than ATSC.

JamesK · 2010-10-31, 04:23 PM

^^^^
Compression does not determine maximum frequency. It's supposed to remove "insignificant" sounds (however, I can certainly hear the difference between MP3 and CD). If there is a significant tone near the cutoff frequency, it should still be there after compression. Also, if lossless compression is used, it shouldn't remove anything. What determines the maximum audio frequency is the sampling rate which, as you show, is higher @ 48 kHz than a CD @ 44 kHz. This means ATSC can pass frequencies up to just below 24 kHz vs 22 for CD. The difference in bandwidth is due to compression, not a lower frequency range. You could run a CD through lossless compression, to get a lower data rate, and then be unable to find any difference after reconstruction.

rob50312 · 2010-10-31, 04:59 PM

Comparing Omni 2 -dt 44 to omni 2 analog 69 and yes there is a large volume difference and less bass from the digital station.Not suprising from a Rogers owned station where they still cant even set the clock on their OTA stations.ASTC sound in general is fantastic.

chengbin · 2010-10-31, 05:26 PM

The ATSC volume is noticeably lower than NTSC on my LG speakers for most channels. Global is an exception, where they sounded similar, and I can't reliably tell. I don't know why.

bentoronto · 2010-11-01, 10:03 AM

PBS-TV Buffalo also has their good-music FM-stereo as a "French" or "Spanish" on 17-2, or thereabouts.

Does (or can?) their TV music feed include HD-FM as on the FM band at 94.5-1 and 94.5-2? I ask this because no one has explained to my grasp about the fidelity standards of these language/music transmissions for music except to repeat "hey, it's digital so it has to be perrrrrfect." HD-FM has its limitations and I wonder how they compare to digital subchannels?

HWP · 2010-11-01, 10:19 AM

On my TV...

17.1 has two sound track options:
A English
B Described Video for hearing impared

17.2 has four sound options:
A English
B WNED FM radio (classical music)
C Described Video
D WNED AM 970 radio (National Public Radio - NPR)

17.3 has three sound options
A English
B WNED FM radio (classical music)
C WNED AM 970 radio (NPR)

I don't have a home theatre but I'd be willing to bet it is not coming in in Dolby quality. I am an NPR listener so I'm very glad to have the radio on my TV channel. I can't get it on my AM radio in the house - only in my car. If I listen on my computer via streaming it eats up bandwidth.

On my TV the sound options are called "Track 1, 2, 3, 4, etc". I just went and checked my TV. The track that is doing the described video on Sesame Street is labled "Espagnol." I would speculate that sometimes the Secondary Audio Program (SAP) is sometimes described video and sometimes Spanish.

Somewhat related...

FYI rf23 virual 51.2 qubo 24hr children's cartoon channel has a every show in both English on the main audio track and Spanish on SAP. For any of you trying to pass on Spanish to the kids, this could be very useful to you.

For whatever reason, my TV often seems to default to Described Video on CITY TV rf53 virutal 57.1. I have to change the track to get rid of the described video.

2010-10-31, 04:59 PM	#72
rob50312 Join Date: Apr 2004 Location: derry + winston Mississauga Posts: 1,300	Comparing Omni 2 -dt 44 to omni 2 analog 69 and yes there is a large volume difference and less bass from the digital station.Not suprising from a Rogers owned station where they still cant even set the clock on their OTA stations.ASTC sound in general is fantastic. __________________ CM 4248 at Buffalo,XG43 at Toronto,M4 at Buffalo,CH 11 yagi at Ham.

2010-11-01, 10:03 AM	#74
bentoronto Join Date: Apr 2009 Location: Toronto (St. Clair/Bathurst) Posts: 398	PBS Buffalo audio feeds PBS-TV Buffalo also has their good-music FM-stereo as a "French" or "Spanish" on 17-2, or thereabouts. Does (or can?) their TV music feed include HD-FM as on the FM band at 94.5-1 and 94.5-2? I ask this because no one has explained to my grasp about the fidelity standards of these language/music transmissions for music except to repeat "hey, it's digital so it has to be perrrrrfect." HD-FM has its limitations and I wonder how they compare to digital subchannels? __________________ Grand Is.(TV ant),BostonNY(FM ant),CN Tower,all in 2 deg; 4221, 60ftRG6, 8dB distr amp SonyHD-FM, Wine.6065, 40ftRG6 Last edited by stampeder; 2010-11-03 at 08:17 PM. Reason: moved to this thread

2010-11-01, 10:19 AM	#75
HWP Join Date: May 2010 Location: Toronto, East York (Greenwood & Mortimer) Posts: 1,143	WNED rf43 virtual 17.1, 2, 3 (+43.8 and 9) On my TV... 17.1 has two sound track options: A English B Described Video for hearing impared 17.2 has four sound options: A English B WNED FM radio (classical music) C Described Video D WNED AM 970 radio (National Public Radio - NPR) 17.3 has three sound options A English B WNED FM radio (classical music) C WNED AM 970 radio (NPR) I don't have a home theatre but I'd be willing to bet it is not coming in in Dolby quality. I am an NPR listener so I'm very glad to have the radio on my TV channel. I can't get it on my AM radio in the house - only in my car. If I listen on my computer via streaming it eats up bandwidth. On my TV the sound options are called "Track 1, 2, 3, 4, etc". I just went and checked my TV. The track that is doing the described video on Sesame Street is labled "Espagnol." I would speculate that sometimes the Secondary Audio Program (SAP) is sometimes described video and sometimes Spanish. Somewhat related... FYI rf23 virual 51.2 qubo 24hr children's cartoon channel has a every show in both English on the main audio track and Spanish on SAP. For any of you trying to pass on Spanish to the kids, this could be very useful to you. For whatever reason, my TV often seems to default to Described Video on CITY TV rf53 virutal 57.1. I have to change the track to get rid of the described video. __________________ OTA, HD7697P, CM7778, Rotator, CM3218, TiVo, HDHomeRun Apple TV, Netflix, Teksavvy, Unblock-us, Wind, MagicJack

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2010-10-31, 01:50 PM	#61
stampeder OTA Forum Moderator Join Date: Jan 2005 Location: North Delta, BC (96Av x 116St) Posts: 23,338	There is no technical reason why ATSC would have lower bass levels than NTSC analogue TV. Personally I find the audio via DTV to be superb. There are lots of reasons why a home user would experience different levels. Sometimes it is the fault of the broadcaster, sometimes it is the gear being used by the consumer. Please give us a detailed list of your home equipment so that we can see if the problem is at your end.

2010-10-31, 01:56 PM	#62
chengbin Join Date: Aug 2008 Posts: 51	I find DTV's audio to be great as well. There is a (sometimes) very noticeable improvement in sound quality going from analog to DTV. I have a LG 50PK550 connected to a Logitech Z-5500 via optical. I have a crappy rabbit ear antenna connected to my TV.

2010-10-31, 02:01 PM	#63
stampeder OTA Forum Moderator Join Date: Jan 2005 Location: North Delta, BC (96Av x 116St) Posts: 23,338	If you test with just the LG's speakers with the Logitech system disconnected is there a difference in the bass level between ATSC and NTSC channels?

2010-10-31, 02:03 PM	#64
chengbin Join Date: Aug 2008 Posts: 51	TV speakers do not produce bass, so I can't tell.

2010-10-31, 02:04 PM	#65
stampeder OTA Forum Moderator Join Date: Jan 2005 Location: North Delta, BC (96Av x 116St) Posts: 23,338	That's not what I'm asking. Can you test with no connection to the Logitech system please? Does the LG's own audio amplifier give equal levels between ATSC and NTSC channels?

2010-10-31, 02:08 PM	#66
chengbin Join Date: Aug 2008 Posts: 51	Let me get back to you when it is my turn to watch TV. Currently the TV is occupied. Are you trying to confirm that ATSC and NTSC's sound level is equal? I don't think so, but I'll verify. I remember increasing my volume when doing that A/B test for OMNI 2 today, and even with the increased volume on the ATSC channel, the NTSC channel has more bass, and it has more bass with a lower "overall" volume.

2010-10-31, 02:10 PM	#67
stampeder OTA Forum Moderator Join Date: Jan 2005 Location: North Delta, BC (96Av x 116St) Posts: 23,338	No problem. Do you connect your TV to your audio system via digital coax, optical, or other?

2010-10-31, 02:13 PM	#68
chengbin Join Date: Aug 2008 Posts: 51	I have it connected via digital optical. BTW I've edited my last post with additional information. Some more information. There was only one time I remember DTV with the right amount of bass, and it was the 2010 Teen Choice Awards. I was expecting bass heavy songs (of course), so I turned my sub volume to the max to compensate for the low bass levels. Later I had to turn it down to normal because it had so much bass it sounded bad.

2010-10-31, 03:39 PM	#69
JamesK Veteran Join Date: May 2009 Location: Mississauga Posts: 5,047	^^^^ One possibility is that analog sounds like it has more bass, because it has less high end. Analog TV sound is FM with 15 kHz maximum modulating frequency and 25 kHz deviation, compared to FM radio's 75 kHz deviation. This will reduce the levels of high frequency audio. The lower deviation will result in higher noise level and the TV's audio circuits may be tuned to filter out that noise and, in the process, further reduce the top end. I don't recall the details for ATSC audio, but IIRC it's better than CD quality, which can contain frequencies approaching 22 kHz and has a much lower noise level.

2010-10-31, 04:06 PM	#70
chengbin Join Date: Aug 2008 Posts: 51	@JamesK I know exactly what you're talking about (I boost treble on my computer speakers), but the difference is large enough that it can't be that. ATSC does not have better sound quality than CD. ATSC's audio is 6 channel AC3 compressed @ 448Kbps (or 384Kbps?) @ 48KHz. CD is uncompressed @ 1411Kbps for 2 channels @ 44.1KHz. AC3 is technically better being 48KHz, translating into 24KHz of usable frequency spectrum, rather than 22KHz of CD. But CD's uncompressed stereo, so it doesn't get better than this for 2 channel sound @ 44.1KHz. Therefore CD is still better than ATSC.

2010-10-31, 04:23 PM	#71
JamesK Veteran Join Date: May 2009 Location: Mississauga Posts: 5,047	^^^^ Compression does not determine maximum frequency. It's supposed to remove "insignificant" sounds (however, I can certainly hear the difference between MP3 and CD). If there is a significant tone near the cutoff frequency, it should still be there after compression. Also, if lossless compression is used, it shouldn't remove anything. What determines the maximum audio frequency is the sampling rate which, as you show, is higher @ 48 kHz than a CD @ 44 kHz. This means ATSC can pass frequencies up to just below 24 kHz vs 22 for CD. The difference in bandwidth is due to compression, not a lower frequency range. You could run a CD through lossless compression, to get a lower data rate, and then be unable to find any difference after reconstruction.

2010-10-31, 05:26 PM	#73
chengbin Join Date: Aug 2008 Posts: 51	The ATSC volume is noticeably lower than NTSC on my LG speakers for most channels. Global is an exception, where they sounded similar, and I can't reliably tell. I don't know why.