File Size Mystery

Help and support for HDHomeRun DVR and HDHomeRun software for Windows 10, Mac, Android, XBox, etc.
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themusj
Posts: 184
Joined: Wed Aug 30, 2017 5:44 pm

File Size Mystery

Post by themusj » Thu Jun 13, 2019 5:44 pm

I have noticed something I am not understanding with my recordings related to file sizes.

I am now at the point where some series I am recording again, waiting for some missing episodes to show up.

So I have a series for example, The Lone Ranger where season 5 episodes I have already recorded are smaller in file size than what was recorded a few months earlier. Same file, same padding, same title, same HDHomeRun tuner and DVR platform, but the episodes are smaller. I ran this Media info on both of them. What can account for the difference? I haven't touched any settings. One is 514MB vs 460MB.

The first recording done in March:
Format: MPEG-TS
File size : 514 MiB
Duration: 30 min 59 s
Overall bit rate mode: Variable
Overall bit rate 2 318 kb/s
FileExtension_Invalid: ts m2t m2s m4t m4s tmf ts tp trp ty

Video
ID 81 (0x51)
Menu ID: 3 (0x3)
Format : MPEG Video
Format version: Version 2
Format profile: Main@Main
Format settings: CustomMatrix / BVOP
Format settings, BVOP: Yes
Format settings, Matrix: Custom
Format settings, GOP: M=3, N=15
Format settings, picture structure: Frame
Codec ID: 2
Duration: 30 min 59 s
Bit rate mode: Constant
Bit rate : 2 009 kb/s
Maximum bit rate: 2 100 kb/s
Width : 720 pixels
Height: 480 pixels
Display aspect ratio: 4:3
Frame rate: 29.970 (30000/1001) FPS
Standard: NTSC
Color space: YUV
Chroma subsampling: 4:2:0
Bit depth: 8 bits
Scan type: Interlaced
Scan order: Top Field First
Compression mode: Lossy
Bits/(Pixel*Frame): 0.194
Time code of first frame: 07:36:24;06
Time code source: Group of pictures header
GOP, Open/Closed: Open
Stream size: 445 MiB (87%)

Audio
ID : 84 (0x54)
Menu ID : 3 (0x3)
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : Dolby Digital
Codec ID : 129
Duration : 30 min 59 s
Bit rate mode : Constant
Bit rate : 192 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Frame rate : 31.250 FPS (1536 SPF)
Bit depth : 16 bits
Compression mode : Lossy
Delay relative to video : -424 ms
Stream size : 42.6 MiB (8%)
Language : English
Service kind : Complete Main

Text #1
ID : 81 (0x51)-CC1
Menu ID : 3 (0x3)
Format : EIA-608
Muxing mode : A/53 / DTVCC Transport
Muxing mode, more info : Muxed in Video #1
Duration : 30 min 59 s
Bit rate mode : Constant
Stream size : 0.00 Byte (0%)
CaptionServiceName : CC1

Text #2
ID : 81 (0x51)-1
Menu ID : 3 (0x3)
Format : EIA-708
Muxing mode : A/53 / DTVCC Transport
Muxing mode, more info : Muxed in Video #1
Duration : 30 min 59 s
Bit rate mode : Constant
Stream size : 0.00 Byte (0%)
Language : English

The recording this week:
Format: MPEG-TS
File size: 460 MiB
Duration: 30 min 58 s
Overall bit rate mode: Variable
Overall bit rate: 2 075 kb/s
FileExtension_Invalid: ts m2t m2s m4t m4s tmf ts tp trp ty

Video
ID: 81 (0x51)
Menu ID: 3 (0x3)
Format : MPEG Video
Format version: Version 2
Format profile: Main@Main
Format settings: CustomMatrix / BVOP
Format settings, BVOP: Yes
Format settings, Matrix: Custom
Format settings, GOP: M=3, N=15
Format settings, picture structure: Frame
Codec ID: 2
Duration: 30 min 58 s
Bit rate mode: Constant
Bit rate: 1 779 kb/s
Maximum bit rate: 1 700 kb/s
Width: 720 pixels
Height: 480 pixels
Display aspect ratio: 4:3
Frame rate: 29.970 (30000/1001) FPS
Standard: NTSC
Color space: YUV
Chroma subsampling: 4:2:0
Bit depth: 8 bits
Scan type: Interlaced
Scan order: Top Field First
Compression mode: Lossy
Bits/(Pixel*Frame): 0.172
Time code of first frame: 04:19:17;00
Time code source: Group of pictures header
GOP, Open/Closed: Open
Stream size: 394 MiB (86%)

Audio
ID : 84 (0x54)
Menu ID : 3 (0x3)
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : Dolby Digital
Codec ID : 129
Duration : 30 min 58 s
Bit rate mode : Constant
Bit rate : 192 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Frame rate : 31.250 FPS (1536 SPF)
Bit depth : 16 bits
Compression mode : Lossy
Delay relative to video : -65 ms
Stream size : 42.5 MiB (9%)
Language : English
Service kind : Complete Main

Text #1
ID : 81 (0x51)-CC1
Menu ID : 3 (0x3)
Format : EIA-608
Muxing mode : A/53 / DTVCC Transport
Muxing mode, more info : Muxed in Video #1
Duration : 30 min 58 s
Bit rate mode : Constant
Stream size : 0.00 Byte (0%)
CaptionServiceName : CC1

Text #2
ID : 81 (0x51)-1
Menu ID : 3 (0x3)
Format : EIA-708
Muxing mode : A/53 / DTVCC Transport
Muxing mode, more info : Muxed in Video #1
Duration : 30 min 58 s
Bit rate mode : Constant
Stream size : 0.00 Byte (0%)
Language : English

Ken.F
Posts: 2088
Joined: Fri Apr 05, 2013 9:20 am
Device ID: 1041A706, 1043EB32, 104BAD9E, 13168DC5, 1322A7AC
Location: West Rockhill, PA

Re: File Size Mystery

Post by Ken.F » Fri Jun 14, 2019 4:20 am

themusj wrote:
Thu Jun 13, 2019 5:44 pm
What can account for the difference? I haven't touched any settings. One is 514MB vs 460MB.
Maybe some of the commercials they are currently running have a lower bitrate. Try editing the commercials out and compare them again.

gtb
Expert
Posts: 3941
Joined: Thu Oct 06, 2011 1:00 pm
Location: Sunnyvale, CA USA

Re: File Size Mystery

Post by gtb » Fri Jun 14, 2019 11:22 am

themusj wrote:
Thu Jun 13, 2019 5:44 pm
I have noticed something I am not understanding with my recordings related to file sizes.
Do both episodes have the same amount of action/movement? With variable bitrate, talking heads takes a lot less bytes to represent than fast action (well, if one is targeting equal quality). In a vary unscientific look of a few of my recordings of a particular (different than yours) series, a 10% variation in file size was not unusual, and I have seen more towards 20% in some specific cases. And another issue that that sometimes a station (or cable operator) will change the targeted bitrate in order to rebalance their system (giving more bandwidth to, say, the primary network subschannel rather than the secondary subchannel).

themusj
Posts: 184
Joined: Wed Aug 30, 2017 5:44 pm

Re: File Size Mystery

Post by themusj » Fri Jun 14, 2019 5:58 pm

Sounds like from what I am reading, since episodes are the same, it was must the stations and not the HDHomerun device or DVR.

I have been opting to keep the large file size episodes over the smaller figuring bigger is better. :-)

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