Flash video total bitrate

[Abstract40]

Hi Everyone,

I'm not a video editor, but a programmer having some critical remarks about flash videos that are produced for us.
A video editor made trailer for us with the following dimensions:

960x540
1500 bitrate using VBR
he usses the VP6 codec

Now he has created trailer of 37 second which have a file size of 12mb to 14mb. I think he's doing something wrong.
Take a look at the information about the video I extracted using mediaInfo.

General
Complete name = C:\temp\trailer.flv
Format = Flash Video
File size = 11.1 MiB
Duration = 37s 172ms
Overall bit rate = 2 512 Kbps

Video
Format = VP6
Duration = 37s 172ms
Bit rate = 1 500 Kbps
Width = 960 pixels
Height = 540 pixels
Display aspect ratio = 16:9
Frame rate mode = Constant
Frame rate = 23.976 fps
Bits/(Pixel*Frame) = 0.121
Stream size = 6.65 MiB (60%)

Audio
Format = MPEG Audio
Format version = Version 1
Format profile = Layer 3
Duration = 37s 172ms
Bit rate mode = Constant
Bit rate = 192 Kbps
Channel(s) = 2 channels
Sampling rate = 44.1 KHz
Bit depth = 16 bits
Stream size = 871 KiB (8%)

A simple calculation show 100% - 60% - 8% = 32% is used for something else. Part of it is used for metadata, but it's really hard to believe metadata takes 3.5mb. With Any Video Converter and memcoder I was already able to reduce the same file to 8Mb with not much differents in the quality.

Just like I said I'm not a video editor, but looking at other flash files created by other video editors this 32% is far to high. Most of the other files have 20% to 8% of the total filesize used for something else then video or audio.

I know it's hard to say what the problem can be, but any idea's or suggestion would help me a lot!

Thanks

[jagabo]

MediaInfo only looks at header information. Try using BitrateViewer which analyzes the actual data and reports the real bitrates. It's possible the encoder was asked to produce a 1500 kbps file (that's why it says 1500 kbps in the header) but it actually produced a higher average bitrate.

[Abstract40]

Hi Jagabo,

Thank you for you quick reply. I downloaded it and check the file. It seems it doesn't have a 1500kbps max bitrate.
It exceed this limit to an average of 2362kbps, but can this explain the 35% of the filesize used for something else?
I mean isn't this kind of data stored in the 60% for video of the particular file?



Another question related to your remark. Can I take the outcome of MediaInfo serious? Is this 35% really used for something else then audio and video or is this only what the header info says about the file?

Best Wishes,
Arian

[poisondeathray]

It seems it doesn't have a 1500kbps max bitrate.

1500 was entered. It wasn't achieved. The encoder overshot. It's not the max bitrate either

Can I take the outcome of MediaInfo serious? Is this 35% really used for something else then audio and video or is this only what the header info says about the file?

It only reports the header, it may or may not be accurate

If you are paranoid, you can use flv extract to see how large the video and audio stream are. There will be a timecodes.txt file as well, but that should only take 1KB or so. The other few KB are overhead for the flv container

[jagabo]

You can't take MediaInfo's bitrate report as the actual average bitrate of the video. The header can say anything. Taking BitrateViewer's reported average of 2362 kbps:

2362 kbps * 37 seconds ~= 87384 Kbits or 10924 KBytes, not the 6.65 MiB reported by MediaInfo. So there's your "missing" bits.

Also, note the difference between MiB and MB:

MiB = 1024 * 1024 Bytes
MB = 1000 * 1000 Bytes

[Bonie81]

@jagabo

it seems like BitRate Viewer fails to read video files with compressed headers.
no sure!

[jagabo]

it seems like BitRate Viewer fail to read video files with compressed headers.
no sure!

I don't know, I'll have to check it out. I know that some MKV tools recently started defaulting to compressed headers.

[Bonie81]

@jagabo

yep...some MKV tools started messing up headers.
ne way BitRate viewer is a nice tool.
Tks!