Method and apparatus for modifying encoded digital video for improved channel utilization

A method of increasing utilization of a first channel when transmitting a multiplex of a set of one or more encoded program streams, each program stream in said set being decodeable by a corresponding decoder, each corresponding decoder including a corresponding decoder buffer, said decoder buffers having a maximum allowable size, said method comprising:

• (a) selecting encoded pictures to be modified, said selecting according to a criterion;
• (b) modifying each said selected encoded picture to form a corresponding modified encoded picture, said modified encoded picture having less data than said selected encoded picture;
• and
• (c) transmitting the corresponding modified encoded pictures through said first channel in place of the selected encoded pictures;
• whereby said criterion includes preventing any underflow of any decoder buffer;
• wherein said encoded program streams include predictively encoded pictures, each said predictively encoded picture having one or more corresponding anchor pictures, each said predictively encoded picture having prediction data and prediction error data, said step of selecting selects predictively encoded pictures that are not anchor pictures, and said step of modifying deletes the prediction error data from each selected encoded picture.

A method of increasing utilization of a first channel when transmitting a multiplex of a set of one or more encoded program streams, each program stream in said set being decodeable by a corresponding decoder, each corresponding decoder including a corresponding decoder buffer, said decoder buffers having a maximum allowable size, said method comprising:

• (a) selecting encoded pictures to be modified, said selecting according to a criterion;
• (b) modifying each said selected encoded picture to form a corresponding modified encoded picture, said modified encoded picture having less data than said selected encoded picture;
• (c) transmitting the corresponding modified encoded pictures through said first channel in place of the selected encoded pictures;
• whereby said criterion includes preventing any underflow of any decoder buffer;
• (d) transmitting the selected encoded pictures;
• (e) determining whether it is possible to decode said selected encoded picture from said first channel;
• and
• (f) whenever possible, decoding said selected encoded picture rather than the corresponding modified encoded picture.

A method of increasing utilization of a first channel when transmitting a multiplex of a set of one or more encoded program streams, each program stream in said set being decodeable by a corresponding decoder, each corresponding decoder including a corresponding decoder buffer, said decoder buffers having a maximum allowable size, said method comprising:

• (a) selecting from at least one of said encoded program streams encoded pictures to be modified that use bidirectional prediction, said selecting being carried out according to a criterion that includes preventing any underflow of any decoder buffer;
• (b) modifying each said selected encoded picture by reducing prediction error data included therein to form a corresponding modified encoded picture having less data than said selected encoded picture;
• and
• (c) transmitting the corresponding modified encoded pictures through said first channel in place of the selected encoded pictures.

A method of increasing utilization of a first channel when transmitting a multiplex of a set of one or more encoded program streams, each program stream in said set being decodeable by a corresponding decoder, each corresponding decoder including a corresponding decoder buffer, said decoder buffers having a maximum allowable size, said method comprising:

• (a) selecting encoded pictures to be modified, said selecting being carried out according to a criterion that includes preventing any underflow of any decoder buffer;
• (b) modifying each said selected encoded picture by reducing prediction error data included therein to form a corresponding modified encoded picture having less data than said selected encoded picture;
• (c) transmitting the corresponding modified encoded pictures through said first channel in place of the selected encoded pictures;
• (d) transmitting the selected encoded pictures;
• (e) receiving the selected encoded pictures and the corresponding modified encoded pictures;
• (f) determining whether to decode said selected encoded pictures;
• and
• (g) decoding said selected encoded pictures in response to a positive determination in step (f);
• wherein said step (f) of determining further includes,
• comparing one or more time stamps associated with the selected encoded pictures with one or more time stamps associated with the corresponding modified encoded pictures.

An apparatus including an encoded digital video modification system for transmitting one or more encoded program streams which are decodeable by a corresponding decoder having a decoder buffer, the decoder buffers having a maximum allowable size, the encoded digital video modification system comprising:

• a program analyzer and modifier configured to receive the one or more encoded program streams and to select encoded pictures to be modified according to a criterion that includes preventing any underflow of any decoder buffer, the program analyzer and modifier further configured to modify each said selected encoded picture to form a corresponding modified encoded picture having less data than said selected encoded picture;
• a primary channel modulator, coupled to the program analyzer and modifier, configured to modulate the corresponding modified encoded pictures onto a primary channel;
• an overflow channel modulator, coupled to the program analyzer and modifier, configured to modulate the selected encoded pictures onto an overflow channel;
• and
• a combiner, coupled to the primary and overflow channel modulators, configured to combine the primary channel with the overflow channel.

An apparatus including an encoded digital video modification system for transmitting one or more encoded program streams which are decodeable by a corresponding decoder having a decoder buffer, the decoder buffers having a maximum allowable size, the encoded digital video modification system comprising:

• a program analyzer and modifier configured to receive the one or more encoded program streams and to select encoded pictures to be modified according to a criterion that includes preventing any underflow of any decoder buffer, the program analyzer and modifier further configured to modify each said selected encoded picture to form a corresponding modified encoded picture having less data than said selected encoded picture;
• a primary packet storage device , coupled to the program analyzer and modifier, configured to store packets that include the corresponding modified encoded pictures;
• an overflow packet storage device, coupled to the program analyzer and modifier, configured to store packets that include the selected encoded pictures;
• and
• a packet multiplexer coupled to and configured to select packets from the primary and overflow packet storage devices and to provide an output multiplex of selected packets.