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dagerson
Beginner

TCS Trancoding bitrates

Hi-

I'm seeing some strange behavior from my TCS', it doesnt have happen all the time and not on all boxes.

Some recordings will transcode at a much higher bitrate than others.  All the aliases are set to the same template and output type, MP4/Medium. 

Here are 2 recordings of the same type, trancoded on the same box.  This is the media info output:

Recording 1:

General / Container Stream # 1

Total Video Streams for this File -> 1

Total Audio Streams for this File -> 1

Video Codecs Used -> AVC

Audio Codecs Used -> AAC LC

File Format -> MPEG-4

Play Time -> 1h 32mn

Total File Size -> 1.04 GiB

Total Stream BitRate -> 1 602 Kbps

Video Stream # 1

Codec (Human Name) -> AVC

Codec (FourCC) -> avc1

Codec Profile -> Baseline@L3.1

Frame Width -> 1 200 pixels

Frame Height -> 490 pixels

Frame Rate -> 29.886 fps

Total Frames -> 166430

Display Aspect Ratio -> 2.449

Scan Type -> Progressive

Colorimetry -> 4:2:0

Codec Settings (Summary) -> 1 Ref Frames

QF (like Gordian Knot) -> 0.088

Codec Settings (CABAC) -> No

Video Stream Length -> 1h 32mn 48s 739ms

Video Stream BitRate -> 1 549 Kbps

Video Stream BitRate Mode -> VBR

Bit Depth -> 24 bits

Video Stream Size -> 1.00 GiB (97%)

Date of Original Encoding -> UTC 2013-03-12 14:09:59

Audio Stream # 1

Codec -> AAC

Codec (FourCC) -> 40

Audio Stream Length -> 1h 32mn 48s 682ms

Audio Stream BitRate -> 48.0 Kbps

Audio Stream BitRate Mode -> CBR

Number of Audio Channels -> 1

Audio Channel's Positions -> C

Sampling Rate -> 48.0 KHz

Bit Depth -> 16 bits

Audio Stream Size -> 31.9 MiB (3%)

Date of Original Encoding -> UTC 2013-03-12 14:09:59

Recording 2:

General / Container Stream # 1

Total Video Streams for this File -> 1

Total Audio Streams for this File -> 1

Video Codecs Used -> AVC

Audio Codecs Used -> AAC LC

File Format -> MPEG-4

Play Time -> 1h 42mn

Total File Size -> 313 MiB

Total Stream BitRate -> 429 Kbps

Video Stream # 1

Codec (Human Name) -> AVC

Codec (FourCC) -> avc1

Codec Profile -> Baseline@L3.1

Frame Width -> 1 200 pixels

Frame Height -> 490 pixels

Frame Rate -> 29.904 fps

Total Frames -> 183080

Display Aspect Ratio -> 2.449

Scan Type -> Progressive

Colorimetry -> 4:2:0

Codec Settings (Summary) -> 1 Ref Frames

QF (like Gordian Knot) -> 0.021

Codec Settings (CABAC) -> No

Video Stream Length -> 1h 42mn 2s 220ms

Video Stream BitRate -> 375 Kbps

Video Stream BitRate Mode -> VBR

Bit Depth -> 24 bits

Video Stream Size -> 274 MiB (88%)

Date of Original Encoding -> UTC 2013-03-12 14:23:10

Audio Stream # 1

Codec -> AAC

Codec (FourCC) -> 40

Audio Stream Length -> 1h 42mn 2s 155ms

Audio Stream BitRate -> 48.0 Kbps

Audio Stream BitRate Mode -> CBR

Number of Audio Channels -> 1

Audio Channel's Positions -> C

Sampling Rate -> 48.0 KHz

Bit Depth -> 16 bits

Audio Stream Size -> 35.0 MiB (11%)

Date of Original Encoding -> UTC 2013-03-12 14:23:10

Any idea what could be causing this?

thanks

Dan

1 REPLY 1
thobonho
Beginner

Hi Dan, I think the answer to your question is in the recording content itself and if there is no much animation, the final file's size after compression can be pretty small even for an 1200x490@30fps video indeed.

This is what video compression is about actually. Only the delta between two frames is stored in the file, so that explains the small size when you record a lecture for instance where the speaker doesn't move much.

Hope this makes sense,

Thomas

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