Adaptive bit rate co-operative transcoding
Methods, systems, and computer readable media can be operable to encode an input video stream into one or more output streams by using information obtained from a first transcoding of the input video stream. During a first encoding of an input video stream, pre-processing, motion estimation, mode decision, and other information can be collected or buffered and can be re-used to encode the input video stream to multiple output video streams at different bitrates, resolutions, and/or frame rates. Motion estimation, macroblock mode decision, and pre-processing data can be manipulated and re-used during the encoding of an input video stream at various resolutions. Data can be re-computed at a new resolution or bitrate to improve visual quality.
1. A computer-implemented method comprising:
receiving an input stream;
determining an optimal bitrate, wherein the optimal bitrate is selected from a group of bitrates, wherein the group of bitrates comprise different bitrates associated with an adaptive bitrate streaming application, and wherein the optimal bitrate comprises the bitrate from which an optimal number of other bitrates from the group of bitrates may be encoded;
encoding the input stream to a first encoded stream, wherein the first encoded stream is encoded at the optimal bitrate, and wherein the first encoded stream is encoded at a highest resolution from a group of resolutions;
storing encoding data generated during the encoding of the input stream to the first encoded stream, wherein the stored encoding data comprises motion vectors associated with one or more blocks of the first encoded stream;
encoding the input stream to a next encoded stream using the stored encoding data, wherein the next encoded stream is encoded at another bitrate of the group of bitrates, and wherein the next encoded stream is encoded at a next resolution in the group of resolutions;
determining whether the next resolution in the group of resolutions is an even divisor of the first resolution;
based upon the determination whether the next resolution in the group of resolutions is an even divisor of the first resolution, selecting a method for determining an optimal motion vector, wherein the selection of a method for determining an optimal motion vector comprises:
if the next resolution in the group of resolutions is an even divisor of the first resolution:
scaling the motion vectors associated with the first encoded stream to generate motion vectors for one or more blocks associated with the next encoded stream; and
calculating a best cost for scaled full-pixel motion vectors, sub-pixel motion vector refinement, and skip and intra-macroblock mode candidates; and
if the next resolution is not an even divisor of the first resolution:
computing a sum of absolute differences for the motion vectors associated with one or more blocks of the first encoded stream;
selecting a best motion vector from the motion vectors associated with the first encoded stream based on the computed sum of absolute differences; and
using the best motion vector in the encoding of the input stream to the next encoded stream.
2. The computer-implemented method of claim 1 , wherein the optimal bitrate is the highest bitrate in the group of bitrates.
3. The computer-implemented method of claim 1 , wherein the optimal bitrate is the median bitrate of the group of bitrates.
4. The computer-implemented method of claim 1 , wherein the stored encoding data comprises pre-processing data, motion estimation data, and mode decision data associated with the first encoded stream.
5. A system, comprising:
an interface operable to be used to send and receive video streams;
a data store operable to store computer program instructions and provide temporary storage for the system; and
a processor operable to execute said computer program instructions, the computer program instructions being operable to cause the processor to:
determine an optimal bitrate, wherein the optimal bitrate is selected from a group of bitrates, wherein the group of bitrates comprise different bitrates associated with an adaptive bitrate streaming application, and wherein the optimal bitrate comprises the bitrate from which an optimal number of other bitrates from the group of bitrates may be encoded;
encode an input video stream to a first encoded stream, wherein the first encoded stream is encoded at the optimal bitrate, and wherein the first encoded stream is encoded at the highest resolution from a group of resolutions;
store encoding data generated during encoding of the input video stream to the first encoded stream, wherein the stored encoding data comprises motion vectors associated with one or more blocks of the first encoded stream;
encode the input video stream to a next encoded stream using the stored encoding data, wherein the next encoded stream is encoded at another bitrate of the group of bitrates, and wherein the next encoded stream is encoded at a next resolution in the group of resolutions;
determine whether the next resolution in the group of resolutions is an even divisor of the first resolution; and
based upon the determination whether the next resolution in the group of resolutions is an even divisor of the first resolution, selecting a method for determining an optimal motion vector, wherein the selection of a method for determining an optimal motion vector comprises:
if the next resolution in the group of resolutions is an even divisor of the first resolution, scale the motion vectors associated with the first encoded stream to generate motion vectors for one or more blocks associated with the next encoded stream; and
if the next resolution in the group of resolutions is not an even divisor of the first resolution:
compute a sum of absolute differences for the motion vectors associated with one or more blocks of the first encoded stream;
select a best motion vector from the motion vectors associated with the first encoded stream based on the computed sum of absolute differences; and
use the best motion vector in the encoding of the input video stream to the next encoded stream.
6. One or more non-transitory computer readable media operable to execute on one or more processors, the computer readable being operable to cause the one or more processors to perform the operations comprising:
receiving an input stream;
determining an optimal bitrate, wherein the optimal bitrate is selected from a group of bitrates, wherein the group of bitrates comprise different bitrates associated with an adaptive bitrate streaming application, and wherein the optimal bitrate comprises the bitrate from which an optimal number of other bitrates from the group of bitrates may be encoded;
encoding the input stream to a first encoded stream, wherein the first encoded stream is encoded at the optimal bitrate, and wherein the first encoded stream is encoded at the highest resolution from a group of resolutions;
storing encoding data during encoding of the input stream to the first encoded stream, wherein the stored encoding data comprises motion vectors associated with one or more blocks of the first encoded stream; and
encoding the input stream to a next encoded stream using the stored encoding data, wherein the next encoded stream is encoded at another bitrate of the group of bitrates, and wherein the next encoded stream is encoded at a next resolution in the group of resolutions;
determining whether the next resolution in the group of resolutions is an even divisor of the first resolution; and
based upon the determination whether the next resolution in the group of resolutions is an even divisor of the first resolution, selecting a method for determining an optimal motion vector, wherein the selection of a method for determining an optimal motion vector comprises:
if the next resolution in the group of resolutions is an even divisor of the first resolution:
scaling the motion vectors associated with the first encoded stream to generate motion vectors for one or more blocks associated with the next encoded stream; and
if the next resolution in the group of resolutions is not an even divisor of the first resolution:
computing a sum of absolute differences for the motion vectors associated with one or more blocks of the first encoded stream;
selecting a best motion vector from the motion vectors associated with the first encoded stream based on the computed sum of absolute differences; and
using the best motion vector in the encoding of the input stream to the next encoded stream.
7. The non-transitory computer readable media of claim 6 , wherein the optimal bitrate is the highest bitrate in the group of bitrates or the median bitrate of the group of bitrates.