Selection of resolutions for seamless resolution switching of multimedia content

1. A source encoder including a processor and a memory readable by the processor where the memory stores an encoding application that directs the processor to receive a primary video stream and to encode the primary video stream into a set of alternative video streams, where the encoding application is characterized by:

select a primary resolution based on a given aspect ratio of the primary video stream;

determine a plurality of height and width combinations for the given aspect ratio from the primary resolution wherein each of the plurality of combinations is derived by:

selecting a first value for a first one of a height or width of a height and width combination,

applying the aspect ratio of the primary stream to the first value, and

rounding a result of the application of the aspect ratio to a nearest integer to determine a second value for a second one of the height and width of a height and width combination,

where the height and width of each combination is an integer number of pixels and is less than the corresponding width and height of the primary resolution and the width and height of the selected combinations have substantially the same aspect ratio as the primary aspect ratio;

determine whether the height and the width of each height and width combination of the plurality of height and width combinations are each whole number fractions of the height and the width of the primary resolution;

select a set of resolutions for the set of alternative video streams from the plurality of height and width combinations by:

determining a plurality of height and width combinations for each of a plurality of alternative aspect ratios, wherein a height and a width for each height and width combination of the plurality of height and width combinations for each of the plurality of alternative aspect ratios of a corresponding height and width combination are both determined to be whole number fractions of the alternative aspect ratio; and

selecting a set of common height and width combinations from the plurality of height and width combinations for the alternative aspect ratios, wherein:

each height and width combination of the set of common height and width combinations has a same particular width; and

the set of common height and width combinations are selected based on a number of alternative aspect ratios at which the plurality of height and width combinations for the alternative aspect ratio comprises a height and width combination with a given width; and

encode a set of alternative video streams from the primary video stream, where each of the alternative video streams is encoded at a different resolution from the set of resolutions and a different bitrate from other video streams in the set of alternative video streams.

2. The source encoder of claim 1 wherein the first value is a width in pixels and the encoder application directs the processor to select the first value for the width by: subtracting a single pixel from a previous width to select the first value for the width.

3. The source encoder of claim 1 wherein the first value is a height in pixels and the encoder application directs the processor to select the first value for the height by: subtracting a single pixel from a previous height to select the first value for the height.

4. The source encoder of claim 1 wherein the selected set of resolutions includes each height and width combination from the plurality of height and width combinations that have a height and a width that is a multiple of 8.

5. The source encoder of claim 1 wherein the set of resolutions selected comprises height and width combinations having a square sample aspect ratio.

6. The source encoder of claim 1 , wherein the encoder application directs the processor to determine whether the height and the width of each height and width combination of the plurality of height and width combinations are each whole number fractions of the height and the width of the primary resolution by determining whether a numerator and a denominator of the whole number fraction are below a given threshold.

7. A method performed by a set of one or more encoding servers of a content distribution system to encode a primary video stream into a set of alternative video streams that are each stored in separate container files comprising a plurality of alternative video streams each having a frame rate and a bitrate, and an audio stream, the method comprising:

selecting a primary resolution based on a given aspect ratio of the primary video stream;

determining a plurality of height and width combinations for the given aspect ratio based upon the primary resolution and the given aspect ratio wherein each of the plurality of combinations is derived by:

selecting a first value for a first one of a height or width for a height and width combination,

applying the aspect ratio of the primary stream to the first value, and

rounding a result of the application of the aspect ratio to a nearest integer to determine a second value for a second one of the height and width of athe height and width combination,

where the height and width of each combination is an integer number of pixels and is less than the corresponding width and height of the primary resolution and the width and height of the selected combinations have substantially the same aspect ratio as the primary aspect ratio;

determining whether the height and the width of each height and width combination of the plurality of height and width combinations are each whole number fractions of the height and the width of the primary resolution;

selecting a set of resolutions for the set of alternative video streams from the plurality of height and width combinations by:

determining a plurality of height and width combinations for each of a plurality of alternative aspect ratios, wherein a height and a width for each height and width combination of the plurality of height and width combinations for each of the plurality of alternative aspect ratios of a corresponding height and width combination are both determined to be whole number fractions of the alternative aspect ratio; and

selecting a set of common height and width combinations from the plurality of height and width combinations for the alternative aspect ratios, wherein:

each height and width combination of the set of common height and width combinations has a same particular width; and

the set of common height and width combinations are selected based on a number of alternative aspect ratios at which the plurality of height and width combinations for the alternative aspect ratio comprises a height and width combination with a given width; and

encoding a set of alternative video streams from the primary video streams where each of the alternative video streams is encoded at a different resolution from the set of resolutions and a different bitrate from other video streams in the set of alternative video streams.

8. The method of claim 7 wherein the first value is a width in pixels and selecting the first value for the width comprises: subtracting a single pixel from a previous width to select the first value for the width.

9. The method of claim 7 wherein the first value is a height in pixels and selecting the first value for the height comprises: subtracting a single pixel from a previous height to select the first value for the height.

10. The method of claim 7 wherein the selected set of resolutions includes each height and width combination from the plurality of height and width combinations that have a height and a width that is a multiple of 8.

11. The method of claim 7 wherein the set of resolutions selected comprises height and width combinations having a square sample aspect ratio.

12. The method of claim 7 , wherein determining whether the height and the width of each height and width combination of the plurality of height and width combinations are each whole number fractions of the height and the width of the primary resolution comprises determining whether a numerator and a denominator of the whole number fraction are below a given threshold.