# Bolt Eating through Storage in OTA confog



## JTHOJNICKI (Nov 30, 2015)

I installed a 3TB Bolt on my OTA antenna and a 3TB Roamio Pro on a Comcast Cablecard back in January. Recordings are pretty equally distributed between the two, but the Bolt HDD is almost 2x as full (72% vs 32%). I understand that some of this may be related to the broadcast compression & encoding. (You'd think something as new as the Bolt could do on-the-fly H.264 or H.265 encoding - My Hauppauge Colossus card can.)

Does this make sense? If so, could I save storage space by recording the local OTA broadcast channels from Comcast? (I didn't think Comcast was compressing locals to H.264.)

I really wish TiVo would introduce a 6-tuner OTA capable Bolt with a 6TB HDD before my free year of TiVo service ends. I'd jump at it in a heartbeat.


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## justen_m (Jan 15, 2004)

JTHOJNICKI said:


> Does this make sense? If so, could I save storage space by recording the local OTA broadcast channels from Comcast? (I didn't think Comcast was compressing locals to H.264.)


Definitely a possibility, even if your cable company is sending you mpeg-2. e.g.
My local CW is about 13Mbps OTA. The same HD channel from CableOne is also mpeg-2, but about 6Mbps. Both are 720p. This is one of the few channels where the difference is this noticeable, but most of the broadcast channels come across with a little less bandwidth via cable. All mpeg-2 for me.

[edit] Try recording the same show on each device, and compare the sizes. Some cable channels may be compressed more compared to OTA than others.


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## BigJimOutlaw (Mar 21, 2004)

It's pretty common of cable to compress the local channels. They don't normally convert them to mpeg4, but they still reduce the bitrate of the channels to make room for more channels.

Yes you most likely would save space by recording the comcast feed, at the expense of video quality.


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## Series3Sub (Mar 14, 2010)

All video delivered digitally OTA or via MVPD's today is ALL compressed using lossy compression. The digital DVR's from all the MVPD's or from 3rd parties like Channel Master only record the digital stream to the HDD and then playback that stream from the HDD and DO NOT perform any encoding or re-encoding on the fly during recording or playback. Encoding was used on DVR's (such as the TiVo S1 and S2) that recorded ANALOG, then needed to encode it to digital to store in the HDD. Believe me, here in L.A. with have quite a few channels that use to look great, but now look diminished because a broadcaster is squeezing 3, 4 or MORE channels along with the main HD channel, and doing it with MPEG2 results in some loss to the HD channel's appearance. It wouldn't have an effect if broadcasters could use MPEG4, but then you would not be able to receive the OTA channel on the TiVo or HDTV itself because TiVo's, Channel Master DVR's, etc., and almost all HDTV's are NOT backward compatible. MPEG for is a hardware issue.

The reason your OTA is sucking up far more space is because broadcast OTA uses the very *in*efficient (and old) MPEG2 encoding, while satellite and cable companies (with a few exceptions such as Dish and DircTV SD channels) use the far more efficient MPEG4 for encoding. MPEG4 can encode data using much smaller files, but with better PQ than MPEG2 all things being equal. So, an MVPD can have far more data in the stream using MPEG4 than compared with MPEG2. This results with your OTA using up far more of the space on the HDD due to MPEG2 and the very same program content on your MSO require far less space on the HDD.

Today, the newer H.265 or HEVC is an improvement over MPEG4 with even more data in even smaller files with no loss of PQ compared to MPEG4 all things being equal. H.265 or HEVC is the ONLY way satellite cos can efficiently deliver Ultra HD (sometimes referred to as "4K") to its subscribers and not require 2 full transponder to do it.


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## rainwater (Sep 21, 2004)

Series3Sub said:


> The reason your OTA is sucking up far more space is because broadcast OTA uses the very *in*efficient (and old) MPEG2 encoding, while satellite and cable companies (with a few exceptions such as Dish and DircTV SD channels) use the far more efficient MPEG4 for encoding.


Cable companies are not using mpeg-4 for locals. At least not in any mass scale. Companies like Charter rarely do anything to the local feed while a few others do compress it but keep it mpeg-2. In fact, it is possible to get a higher quality mpeg-2 feed over cable due to the fact that it comes over fiber to the cable company usually (and isn't limited by subchannels OTA). However, this is also rare.


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## SomeRandomIdiot (Jan 7, 2016)

JTHOJNICKI said:


> I installed a 3TB Bolt on my OTA antenna and a 3TB Roamio Pro on a Comcast Cablecard back in January. Recordings are pretty equally distributed between the two, but the Bolt HDD is almost 2x as full (72% vs 32%). I understand that some of this may be related to the broadcast compression & encoding. (You'd think something as new as the Bolt could do on-the-fly H.264 or H.265 encoding - My Hauppauge Colossus card can.)
> 
> Does this make sense? If so, could I save storage space by recording the local OTA broadcast channels from Comcast? (I didn't think Comcast was compressing locals to H.264.)
> 
> I really wish TiVo would introduce a 6-tuner OTA capable Bolt with a 6TB HDD before my free year of TiVo service ends. I'd jump at it in a heartbeat.


Does an OTA TiVo record the full 19.2Mbps Stream OTA or only the selected program?


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## SomeRandomIdiot (Jan 7, 2016)

rainwater said:


> Cable companies are not using mpeg-4 for locals. At least not in any mass scale. Companies like Charter rarely do anything to the local feed while a few others do compress it but keep it mpeg-2. In fact, it is possible to get a higher quality mpeg-2 feed over cable due to the fact that it comes over fiber to the cable company usually (and isn't limited by subchannels OTA). However, this is also rare.


As discussed in other threads, though possible, in practice it only really happens in smaller markets where 2 Networks are on 1 RF Channel.


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## atmuscarella (Oct 11, 2005)

SomeRandomIdiot said:


> Does an OTA TiVo record the full 19.2Mbps Stream OTA or only the selected program?


OTA TiVos record channels not frequencies. So unless someone still has a channel using all of a single frequency the stream being recorded is something less than 19.2 Mbps. I haven't had any frequencies with only one channel on them for several years. The size of my HD recordings for a 1 hour prime time show vary allot. I see a low of less than 3Gbs and a high of over 6Gbs for an hour show.


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## JoeKustra (Dec 7, 2012)

atmuscarella said:


> OTA TiVos record channels not frequencies.  So unless someone still has a channel using all of a single frequency the stream being recorded is something less than 19.2 Mbps. I haven't had any frequencies with only one channel on them for several years. The size of my HD recordings for a 1 hour prime time show vary allot. I see a low of less than 3Gbs and a high of over 6Gbs for an hour show.


Always exceptions.
https://en.wikipedia.org/wiki/WYOU
https://en.wikipedia.org/wiki/WBRE-TV

My DMA. But my cable feed does add a subchannel. I still get 18.5Mbps on both.


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## SomeRandomIdiot (Jan 7, 2016)

atmuscarella said:


> OTA TiVos record channels not frequencies. So unless someone still has a channel using all of a single frequency the stream being recorded is something less than 19.2 Mbps. I haven't had any frequencies with only one channel on them for several years. The size of my HD recordings for a 1 hour prime time show vary allot. I see a low of less than 3Gbs and a high of over 6Gbs for an hour show.


Ok, then that is eliminated as a possibility of why the OTA recordings are MUCH larger than cable equivalent. Clearly the cable system must be rate shaping/bit starving the OTA channel.

If the OP is using the OTA Tivo to record OTA and the Comcast Cable TiVo to record Cable Channels (which would seem logical), then the MPEG4 (he listed the Chicago DMA) of the Cable Channels would explain why the Cable TiVo has 50% less space used than the OTA TiVo recording MPEG2.


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## rainwater (Sep 21, 2004)

SomeRandomIdiot said:


> Ok, then that is eliminated as a possibility of why the OTA recordings are MUCH larger than cable equivalent. Clearly the cable system must be rate shaping/bit starving the OTA channel.
> 
> If the OP is using the OTA Tivo to record OTA and the Comcast Cable TiVo to record Cable Channels (which would seem logical), then the MPEG4 (he listed the Chicago DMA) of the Cable Channels would explain why the Cable TiVo has 50% less space used than the OTA TiVo recording MPEG2.


Comcast doesn't use mpeg-4 for locals that I know of. Unless his market is some type of test system.


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## SomeRandomIdiot (Jan 7, 2016)

rainwater said:


> Comcast doesn't use mpeg-4 for locals that I know of. Unless his market is some type of test system.


I never said it did. Reread my post.

Cable Channels = Discovery, ESPN, Bravo, Disney, TNT, TBS

OTA Channels = CBS, NBC, ABC, FOX, PBS


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## rainwater (Sep 21, 2004)

SomeRandomIdiot said:


> I never said it did. Reread my post.
> 
> Cable Channels = Discovery, ESPN, Bravo, Disney, TNT, TBS
> 
> OTA Channels = CBS, NBC, ABC, FOX, PBS


Re-read the first post. The poster is talking about OTA recordings and the locals on Comcast. Those recordings would not be affected by mpeg-4.


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## SomeRandomIdiot (Jan 7, 2016)

rainwater said:


> Re-read the first post. The poster is talking about OTA recordings and the locals on Comcast. Those recordings would not be affected by mpeg-4.


You might want to check yourself and re read the OPs 2nd Paragraph. If realize you need to use some logic which is often in short supply, but if he is not recording OTAs via Comcast now, what Must he be recording on the Comcast TiVo?

Easier than many Aptitude Questions.

Apology accepted.


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