4-byte limit
Radium
http://groups.google.com/group/sci.electronics.basics/msg/b134a331423ab42e?hl=en&
:
> You cannot
> compress any amount of data smaller than 4 bytes. Look up the wmv
> spec. Even if the picture was a blank screen it would take more than 4
> bytes.
Does the 4-byte limit also apply to WMA audio? Does it apply to other
formats?
How is it that a 44,100 hz WMA file can have a bit-rate of 20kbps?
4 bytes = 32 bits
44,100/32 = 1378.125
Does this mean a WMA file that is monoaural and 44.1 Khz can have a
minimum bit-rate of 1378 or 1379 bits per second?
Thanks,
Radium
Ron Capik
> < ...snip... >
>
> How is it that a 44,100 hz WMA file can have a bit-rate of 20kbps?
>
> 4 bytes = 32 bits
>
> 44,100/32 = 1378.125
>
> Does this mean a WMA file that is monoaural and 44.1 Khz can have a
> minimum bit-rate of 1378 or 1379 bits per second?
>
> Thanks,
>
> Radium
But your units come out as samples per bit second.
Later...
--
Radium
Ron Capik wrote:
> But your units come out as samples per bit second.
Okay. But is it true that the file size cannot be compressed to more
than 4-bytes?
I am really confused.
Michael Walraven
* 16 bits/ sample (normal CD quality) = 1,411,200 bits per second.
using a compression scheme to get to 20,000 bits/sec is a compression ratio
of 70.56 which is why 20kbbs will not sound very good.
From WMP-11, ripping options are
WMA lossless, using 470,000 to 940,000 bbs this sounds identical to the
origional as the resulting bit stream is identical (lossless) to the
origional.
The maximum compression scheme WMP11 provides is WMA set to 48,000 bits/sec
which is ok on a portable player or in a noisy car
but even my tin ears can hear the degradation at this setting.
Don't know what you are using to get 20,000 bits/sec but it ought to result
in pretty bad sound.
(sound capture program in XP can be set to some pretty low rates and they
sound REALLY bad).
Michael
"Ron Capik" <r.c...@worldnet.att.net> wrote in message
news:45412344...@worldnet.att.net...
Radium
Michael Walraven wrote:
> 44,100 samples/sec per channel * 2 channels = 88200 samples/sec
>
> * 16 bits/ sample (normal CD quality) = 1,411,200 bits per second.
>
> using a compression scheme to get to 20,000 bits/sec is a compression ratio
> of 70.56 which is why 20kbbs will not sound very good.
>
> From WMP-11, ripping options are
> WMA lossless, using 470,000 to 940,000 bbs this sounds identical to the
> origional as the resulting bit stream is identical (lossless) to the
> origional.
> The maximum compression scheme WMP11 provides is WMA set to 48,000 bits/sec
> which is ok on a portable player or in a noisy car
> but even my tin ears can hear the degradation at this setting.
>
> Don't know what you are using to get 20,000 bits/sec but it ought to result
> in pretty bad sound.
> (sound capture program in XP can be set to some pretty low rates and they
> sound REALLY bad).
>
> Michael
I don't mind the artifacts associated with WMA as long as the
sample-rate is as long as:
1. The sample rate is at least 44.1 khz
2. Was at least 44.1 khz prior to compression
3. The WMA's sample rate is the same as the sample rate of the audio
when it was uncompressed
4. The audio is monoaural
As with any digital audio, I prefer a sample-rate of at least 44.1 khz.
I do not like aliasing at all. I dislike all audio compression schemes
other than WMA. I can't stand the artifacts associated with MP3s,
especially low bit-rate stereo MP3s where the audio loses its clarity
of location.
As with all audio. I like monoaural only.
BTW, I never got my most important question answered. What exactly is
the 4-byte limit that a poster named "Tom P." described in
http://groups.google.com/group/sci.electronics.basics/msg/b134a331423ab42e?hl=en&
????
Does this mean the WMA/WMV file cannot have a file size less than
4-bytes no matter how small the color-resolution or how short the
song/movie is?
Michael Walraven
it.
WMA files are wrapped in a ASF file structure which has the format:
Object GUID 16 Bytes (128 bits)
Object Size 8 Bytes (64 bits)
Object data {as many as needed}
so as a minimum, not knowing what type of WMA file is involved 192 bits (24
bytes) are required. (probably somewhat more)
if you are really interested look on the microsoft MSDN (Microsoft Developer
Network) web sites for 'ASF' . Lots of stuff to keep the curious occupied.
Michael
"Radium" <gluc...@excite.com> wrote in message
news:1161901005....@b28g2000cwb.googlegroups.com...
Radium
Michael Walraven wrote:
> An empty wma file will have some overhead even if there is no 'data' within
> it.
> WMA files are wrapped in a ASF file structure which has the format:
>
> Object GUID 16 Bytes (128 bits)
> Object Size 8 Bytes (64 bits)
> Object data {as many as needed}
>
> so as a minimum, not knowing what type of WMA file is involved 192 bits (24
> bytes) are required. (probably somewhat more)
Okay. What about WMV? What is WMV's minimum? Is it 4 bytes as "Tom P"
says?
BTW, is WMV really the video-equivalent of WMA? I hope so but I suspect
not.
Richard Crowley
> Michael Walraven wrote:
>> An empty wma file will have some overhead even if there is no 'data'
>> within
>> it.
>> WMA files are wrapped in a ASF file structure which has the format:
>>
>> Object GUID 16 Bytes (128 bits)
>> Object Size 8 Bytes (64 bits)
>> Object data {as many as needed}
>>
>> so as a minimum, not knowing what type of WMA file is involved 192 bits
>> (24
>> bytes) are required. (probably somewhat more)
>
> Okay. What about WMV? What is WMV's minimum?
WMV is also ASF, same rules apply.
> Is it 4 bytes as "Tom P" says?
4 bytes of WHAT?
Total file length? (Definitely not)
Data length? (What's the point?)
> BTW, is WMV really the video-equivalent of WMA?
They are both produced exclusively by the Windows Media Encoder.
Does that give you a strong hint?
> I hope so but I suspect not.
Why? (That is a rhetorical question)
Radium
Michael Walraven wrote:
> An empty wma file will have some overhead even if there is no 'data' within
> it.
> WMA files are wrapped in a ASF file structure which has the format:
>
> Object GUID 16 Bytes (128 bits)
> Object Size 8 Bytes (64 bits)
> Object data {as many as needed}
>
> so as a minimum, not knowing what type of WMA file is involved 192 bits (24
> bytes) are required. (probably somewhat more)
Okay. What about WMV? What is WMV's minimum? Is it 4 bytes as "Tom P"
says?
BTW, is WMV really the video-equivalent of WMA? I hope so but I suspect
not.
> if you are really interested look on the microsoft MSDN (Microsoft Developer
Michael Walraven
Michael
"Radium" <gluc...@excite.com> wrote in message
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