Apparatus, a method and a computer program for video coding and decoding

1. A method comprising:

encoding video media content into at least a first representation and a second representation, wherein:

the first representation comprises a switchable inter-coded picture, wherein the switchable inter-coded picture comprises a first characteristic that no pictures preceding the switchable inter-coded picture in decoding order are used as reference pictures for non-switchable pictures following the switchable inter-coded picture in decoding order; and

the second representation comprises one or more decoder reset pictures aligned with switchable inter-coded pictures of the first representation,

wherein a frame rate of the second representation is smaller than or equal to a frame rate of the first representation and resolutions of the first and the second representations are equal or substantially equal,

wherein the first representation and the second representation are encoded to enable decoding of a decoder reset picture of the second representation, followed by decoding of pictures of the first representation that are subsequent to a switchable inter-coded picture of the first representation that corresponds to the decoder reset picture, without the corresponding switchable inter-coded picture having been decoded.

2. An apparatus comprising at least one processor and at least one non-transitory memory including computer program code for one or more programs, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

encode video media content into at least a first representation and a second representation, wherein:

the first representation comprises a switchable inter-coded picture, wherein the switchable inter-coded picture comprises a first characteristic that no pictures preceding the switchable inter-coded picture in decoding order are used as reference pictures for non-switchable pictures following the switchable inter-coded picture in decoding order; and

the second representation comprises one or more decoder reset pictures aligned with switchable inter-coded pictures of the first representation,

wherein a frame rate of the second representation is smaller than or equal to a frame rate of the first representation and resolutions of the first and the second representations are equal or substantially equal,

wherein the first representation and the second representation are encoded to enable decoding of a decoder reset picture of the second representation, followed by decoding of pictures of the first representation that are subsequent to a switchable inter-coded picture of the first representation that corresponds to the decoder reset picture, without the corresponding switchable inter-coded picture having been decoded.

3. The apparatus according to claim 2 , wherein the switchable inter-coded picture comprises a second characteristic that the switchable inter-coded picture is predicted at least from zero or more previous switchable inter-coded pictures or from a previous random access picture in decoding order.

4. The apparatus according to claim 2 , wherein the apparatus is further caused to indicate, in or along a bitstream corresponding to the first representation, suitability of content of the first and second representations for switching between the first representation and the second representation in decoding.

5. The apparatus according to claim 2 , wherein the decoder reset picture is configured to be encoded as a broken link access picture type comprising no leading pictures following the broken link access picture or as an independent decoding refresh picture.

6. A method comprising:

receiving at least one bitstream corresponding to a first representation of encoded video media content, the first representation comprising a switchable inter-coded picture, wherein the switchable inter-coded picture comprises a first characteristic that no pictures preceding the switchable inter-coded picture in decoding order are used as reference pictures for non-switchable pictures following the switchable inter-coded picture in decoding order;

receiving, from or along the at least one bitstream, an indication about suitability of switching between the first representation and a second representation of the encoded video media content in decoding, wherein the second representation comprises one or more decoder reset pictures aligned with switchable inter-coded pictures of the first representation, wherein a frame rate of the second representation is smaller than or equal to a frame rate of the first representation and resolutions of the first and the second representations are equal or substantially equal;

receiving at least one decoder reset picture of the second representation; and

decoding the at least one decoder reset picture of the second representation, followed by decoding of pictures of the first representation that are subsequent to a switchable inter-coded picture of the first representation that corresponds to the at least one decoder reset picture, without the corresponding switchable inter-coded picture having been decoded.

7. An apparatus comprising at least one processor and at least one non-transitory memory including computer program code for one or more programs, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

receive at least one bitstream corresponding to a first representation of encoded video media content, the first representation comprising a switchable inter-coded picture, wherein the switchable inter-coded picture comprises a first characteristic that no pictures preceding the switchable inter-coded picture in decoding order are used as reference pictures for non-switchable pictures following the switchable inter-coded picture in decoding order;

receive, from or along the at least one bitstream, an indication about suitability of switching between the first representation and a second representation of the encoded video media content in decoding, wherein the second representation comprises one or more decoder reset pictures aligned with switchable inter-coded pictures of the first representation, wherein a frame rate of the second representation is smaller than or equal to a frame rate of the first representation and resolutions of the first and the second representations are equal or substantially equal;

receive at least one decoder reset picture of the second representation; and

decode at least one decoder reset picture of the second representation, followed by decoding of pictures of the first representation that are subsequent to a switchable inter-coded picture of the first representation that corresponds to the at least one decoder reset picture, without the corresponding switchable inter-coded picture having been decoded.

8. The apparatus according to claim 7 , wherein the switchable inter-coded picture comprises a second characteristic that the switchable inter-coded picture is predicted at least from zero or more previous switchable inter-coded pictures or from a previous random access picture in decoding order.

9. The apparatus according to claim 7 , wherein the apparatus is further caused to request, in response to a pause in a playback of the decoded first representation, the at least one decoder reset picture of the second representation.

10. The apparatus according to claim 7 , wherein the apparatus is further caused to request, in response to a viewport switch, the at least one decoder reset picture of the second representation.

11. The apparatus according to claim 10 , wherein the viewport switch takes place from a first viewport to a second viewport, and wherein the first representation covers the first viewport, and wherein the apparatus is further caused to receive a second bitstream corresponding to a third representation of the encoded video media content, the third representation representing the second viewport.

12. The apparatus according to claim 7 , wherein the apparatus is further caused to request, in response to a viewpoint switch, the at least one decoder reset picture of the second representation.

13. The apparatus according to claim 12 , wherein the viewpoint switch takes place from a first viewpoint to a second viewpoint, and wherein the first representation covers the first viewpoint, and wherein the apparatus is further caused to receive a second bitstream corresponding to a third representation of the encoded video media content, the third representation representing the second viewpoint.

14. The apparatus according to claim 7 , wherein the apparatus is further caused to:

decode, in response to a re-start of a playback, a decoder reset picture substantially timely corresponding to the re-start; and

switch to decode pictures of the first representation following, in decoding order, a switchable inter-coded picture of the first representation, which is temporarily aligned with the decoder reset picture substantially timely corresponding to the re-start.

15. The apparatus according to claim 7 , wherein the apparatus is further caused to:

request, in response to a pause in a playback of the decoded first representation, a plurality of decoder reset pictures of the second representation based on available bandwidth.

16. The apparatus according to claim 7 , wherein the apparatus is further caused to:

request the at least one decoder reset picture of the second representation for carrying out bitrate adaptation between the first representation and a third representation.

17. The apparatus according to claim 16 , wherein a bitrate switch takes place from a first bitrate to a second bitrate, and wherein the first representation corresponds to the first bitrate, and wherein the apparatus is further caused to receive a second bitstream corresponding to the third representation of the encoded video media content, the third representation representing the second bitrate.

18. The apparatus according to claim 7 , wherein the apparatus is further caused to:

extract at least one switchable inter-coded picture from a first extractor track or representation; and

extract the at least one decoder reset picture from a second extractor track or representation.

19. A computer program product comprises at least one non-transitory computer-readable storage medium having computer executable program code instructions stored therein, the computer executable program code instructions comprising program code instructions configured, upon execution, to:

receive at least one bitstream corresponding to a first representation of encoded video media content, the first representation comprising a switchable inter-coded picture, wherein the switchable inter-coded picture comprises a first characteristic that no pictures preceding the switchable inter-coded picture in decoding order are used as reference pictures for non-switchable pictures following the switchable inter-coded picture in decoding order;

receive, from or along the at least one bitstream, an indication about suitability of switching between the first representation and a second representation of the encoded video media content in decoding, wherein the second representation comprises one or more decoder reset pictures aligned with switchable inter-coded pictures of the first representation, wherein the frame rate of the second representation is smaller than or equal to a frame rate of the first representation and resolutions of the first and the second representation are equal or substantially equal;

receive at least one decoder reset picture of the second representation; and

decode the at least one decoder reset picture of the second representation, followed by decoding of pictures of the first representation that are subsequent to a switchable inter-coded picture of the first representation that corresponds to the at least one decoder reset picture, without the corresponding switchable inter-coded picture having been decoded.