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.ft title General Overview\n
\n
.ft sdout mpeg_bits
is a tool for monitoring and modifying the bitrate of MPEG streams.
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.ft sdout mpeg_bits
consists of three separate windows. The playback window displays the video
encoded in the given MPEG stream, and can be used to select regions to re-encode.
The control window provides VCR-like controls to control the playing of the video.
From left to right, its buttons are: step-back-to-previous-GOP, stop, play, and
step forward. The information window provides feedback on the bit allocation for
the given stream, and provides an interface for producing a specifics file to
modify the bitrate in subsequent encodings.
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The information window contains the following items, from the top down:
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* The menu bar, containing the
.ht .filHelp File
,
.ht .ediHelp Edit
,
and Help menus.
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* The bit field. This is a representation of how the bits are allocated, macroblock by
macroblock, in the current frame. As the legend indicates at the bottom, a more intense
color indicates a larger number of bits used to encode that block. Empty blocks
represent skipped blocks. To get the exact size of a block in the bit field,
click on it with the middle mouse button. The
size will appear in the upper right corner of the bit field. The bit field also provides
the interface for selecting which macroblocks are to be
included in an
.ht .ediHelp edit.
\n
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* The frame information field. This gives the number (starting at 0), type, and size of the
current frame.
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* The relative frame sizes field. This graphically represents the size and type of the past
few frames, scrolling from the right (the red line indicates the current frame). To get the exact
size of a particular frame, click on it's rectangle with the middle mouse button: the size will
appear at the top right of the bit field.
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* The bitrate gauge. This indicates the actual bitrate over the past second of video, denoted
by a segmented black line, vs. the target bitrate for the stream, which is indicated by the
horizontal red line. The vertical red line at right indicates the current frame. Note this is
only active once a second of video has been played.
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For a step-by-step walkthrough of how to use
.ft sdout mpeg_bits
to produce a specifics file that alters the encoding, see
.ht .sesHelp Sample Session.
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