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| In order to get your media ready for
streaming, you will need to capture
it into a digital format and then
encode it to a streaming format. |
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| Capturing
Your Media Content |
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| Capturing is the process of recording
audio and video from a source to a hard drive in a
digital format. The process starts with the source
format, which can be audio or video. That source is
then played on the deck that supports its format.
The deck is connected to a capture card, which receives
the playback information and digitizes it with the
help of capture software. The capture software takes
the input from the capture card and saves to the hard
drive. |
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A) What equipment will I need?
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Equipment needed includes playback decks and
capture cards. The playback decks include
audiotape, VHS, Beta and DV. The capture card
will depend on what your playback deck is.
For DV formats you can use FireWire/IEEE1394.
The advantage of FireWire is it gives you
device control of the playback deck. All new
Macintosh computers come with FireWire built
in and you can buy FireWire cards for PC's
at a low cost. Many DV decks have analog inputs
that can be used for analog formats like audiotape,
VHS and Beta. By playing the analog format
through the DV deck you can capture using
FireWire, which reduces the cost and amount
of equipment needed to capture if you have
multiple source formats.
For analog formats like audiotape, VHS and
Beta you can use an analog capture card. The
capture card can have audio and video jacks
in a range of formats from RCA to XLR, BNC
and S-video connectors. Many companies make
capture cards including Winnov,
Osprey and
Pinnacle.
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B) What software will I need?
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Capture software can be video editing software
like Apple's Final Cut Pro and Adobe's Premier
or encoding software such as the Windows Media
Encoder and the Real Producer Plus. Capturing
with either the Windows Media Encoder or Real
Producer Plus will save video in the encoder's
format. Using encoder software to capture
will not produce the best quality encodes.
With video editing software the source is captured
to your hard drive, and you can make any edits
or changes. Then export your source clip into
a format that the encoder software will be
able to read. In some cases you can export
directly into your target format from the
editing software, but in most cases software
made specifically for encoding will do a better
job. When exporting video to be encoded we
recommend exporting as an .AVI. For maximum
quality and best usage of storage space we
recommend the Indeo Video 5 codec for the
video portion. The codec is available for
both Mac and PC from Apple's web site. Export
at the same frame size and frame rate as the
capture. Set key frames to every 15 frames
and do not limit the data rate of the video.
For the audio portion we recommend uncompressed
mono or stereo depending on your needs.
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| Encoding
Your Media Content |
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| Encoding is the process of converting
audio or video into a streaming format. The process
starts with the source. The source can either be a
file or a live feed. The encoder is set to take the
source and format it for a specific bit rate, frame
rate and frame size. As the source is processed it
is saved to a file and/or sent as a stream to a server
depending on if the content is for on-demand or live
use. |
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A) What software do I need?
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Encoding software will depend on your target
format. For Window’s Media, we recommend the
Window’s Media 9 Encoder.The Windows Media
Encoder is free and only available for PC.
For Real, we recommend using the
Real Producer Plus. The Real Producer
Plus is available for both MAC and PC for
a price; there also is a free basic version,
but it lacks many features. For QuickTime
you will need the
Sorenson Video 3 Pro codec,
QDesign audio codec, Sorenson Squeeze
or
Media Cleaner 6. All of the necessary
QuickTime software is available for both MAC
and PC at a cost. For MPEG encoding we recommend
the
Ligos LSX-MPEG encoder. Here are some
other useful software for transcoding formats;
FlaskMPEG,
QuickTime
Pro and avi2mpg1.
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B) How to encode video?
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Most video codecs encode for what changes frame
to frame. In general low motion content and
static camera work will produce a higher quality
encode. Since there is a limit to the data
rate of the video set by the target audience,
codecs maintain that data rate by reducing
colors, lowering the frame rate and reducing
image clarity.
The target audience will establish the bit
rate, which in turn determines the frame size
and frame rate. For low bit rates (20 - 45Kbps)
we recommend a frame rate of 5 to 7 frames
per second (fps), and a frame size of 160x120
going no larger than 192x144. For high bit
rates (80 - 350Kbps) we recommend a frame
rate of 15fps and a maximum frame size of
320x240. Many encoders have a variable bit
rate (VBR) option; we recommend only using
VBR for download and never for streaming content.
VBR can cause excessive buffering and doesn't
provide a consistent data rate.
For Windows Media, we recommend the Windows
Media Video 8 codec. Windows Media supports
both single and multiple bit rate encoding.
When doing a multiple bit rate encode using
the 8 codec, be aware the Macintosh version
of the Windows Media player only supports
single bit rate encoding using the 8 codec.
If you want a multiple bit rate encode that
will work on the Macintosh use the 7 codec.
For Real, we recommend the Real 8 codec. Real
Media also supports both single and multiple
bit rate encoding. Be careful when doing multiple
bit rate encoding using Real, for each bit
rate selected the encoder will do one to two
reduced rates, which can cause very large
file sizes. For example, if you encode at
34 and 150Kbps the file will have 5 bit rates
in it, 20.4, 25.5, 34, 112.5 and 150Kbps.
We recommend using the 2-pass encoding option
in the Real Producer Plus for higher quality
encodes, but not in Media Cleaner because
the 2-pass option is linked to the VBR option.
For QuickTime, we recommend the Sorenson Video
3 Pro codec. QuickTime only supports single
bit rate encodes. The Sorenson 3 codec is
the least user friendly. In the options of
the Sorenson 3 codec be sure to check image
smoothing, set key frames to none or rare
and always do constant bit rate encode (CBR)
for streaming. The encoders will have an option
to prepare for streaming. For streaming content
be sure to select hinted streaming and set
the payload settings to use QuickTime. For
download content select fast start.
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C) How to encode audio?
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The audio codec used in encoding will depend
on the target format and if the audio is voice,
music or a combination. For Windows Media,
we recommend the Windows Media Audio V8 for
both voice and music content. For Real, we
recommend the voice codec for voice only content
and the Real Audio 8 codec for music or combination.
For QuickTime, we recommend the
QDesign codec for most voice and music.
If the clip is audio and voice only, the Qualcomm
PureVoice can also be used.
When encoding audio choosing mono or stereo
has a significant effect on quality. If you
encode at 20Kbps stereo the overall quality
will be 10Kbps, because the bit rate is split
for each audio channel. We recommend encoding
voice anywhere from 5 to 20Kbps mono. For
music encode at 10 to 64Kbps mono or 32 to
128Kbps when stereo is necessary.
Tip: Before encoding audio use a compressor/limiter
to reduce the range of the audio. The encoder
will cut out the high and low end. Using the
compressor/limiter will insure more of your
original audio is translated into the encoded
format.
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