Digital video recorder having live-off-disk buffer for receiving missing portions of buffered events

1. A method of receiving content over a content delivery system, the method comprising:

receiving a request to initiate a rewind operation on content associated with an event, wherein the content is received over a content delivery system;

determining that at least a portion of the content associated with the event is not available in a local storage, wherein a live-off-disk (LOD) buffer is configured to buffer content previously received over the content delivery system for rendering during rewind operations;

communicating a message over the content delivery system to a headend, the message specifying a delivery in reverse of normal chronological frame order, and the message comprising a request for the delivery of the portion of the content associated with the event that is locally unavailable;

by a digital video recorder (DVR) device, in response to the message, receiving from the headend the delivery as a stream, in reverse of normal chronological frame order of the requested content, wherein the headend spools the requested content for the delivery;

rendering by the DVR device, without locally storing a file of the requested content received as the stream, and without updating an index file of the requested content, the stream of the delivery of the requested content contemporaneously as it is spooled by the headend, in reverse of normal chronological frame order as received during the rewind operation;

communicating a message over the content delivery system to the headend to deliver the requested content in normal chronological frame order; and

rendering the requested content received from the headend in normal chronological frame order;

wherein upon reaching a point in the rendering of the content at which the content is available from the LOD buffer, the source of the content for rendering is switchable from the headend to the LOD buffer such that rendering subsequent content, in normal chronological frame order, is from the LOD buffer.

2. The method of claim 1 wherein communicating the message is performed prior to reaching a point in the rendering of the content at which no more of the content is available from the LOD buffer.

3. The method of claim 1 wherein communicating the message is performed when a point in the rendering of the content is reached at which no more of the content is available from the LOD buffer.

4. The method of claim 1 wherein determining that the request includes a request for content that is not available in a local storage comprises determining that all of the event is not available in the LOD buffer.

5. The method of claim 4 further comprising determining that all of the event is not available in the LOD buffer by consulting an electronic program guide to identify a start and end time for the event.

6. A set top box, comprising:

a front-end for receiving content over a content delivery system;

a digital video recorder (DVR) subsystem for selectively recording content received over the content delivery system, said DVR subsystem including a storage medium for storing the recorded content and a live-off-disk (LOD) buffer; and

a processor operatively associated with the front-end and the DVR subsystem and being configured to cause communication to be established with a headend over the content delivery system if it is determined that at least a portion of the content associated with the event is not available in the storage medium, wherein the LOD buffer is configured to buffer content previously received for rendering during rewind operations,

wherein the communication includes a message specifying a delivery in reverse of normal chronological frame order, the message comprising a request for the delivery of the portion of the content associated with the event that is locally unavailable,

wherein the headend spools the requested content for the delivery;

wherein the front-end is configured for receiving from the headend the delivery as a stream in reverse of normal chronological frame order of the requested content when the communication includes a request for a rewind operation, and the front-end is configured for receiving the requested content in normal chronological frame order from the headend when the communication includes a request for delivery to be in normal chronological frame order,

wherein the DVR subsystem is configured to render, without locally storing a file of the requested content received as the stream, and without updating an index file of the requested content, the stream of the requested content contemporaneously as it is spooled from the headend, in the frame order received from the headend; and

wherein upon reaching a point in the rendering of the content at which a second portion of the content is available from the LOD buffer, the source of the content for rendering is switchable from the headend to the LOD buffer such that rendering subsequent content, in normal chronological frame order, is from the LOD buffer.

7. The set-top box of claim 6 wherein the processor is further configured to cause the communication to be established upon the user request.

8. The set-top box of claim 6 wherein the processor is further configured to cause the communication to be established when the user-initiated rewind operation reaches a point in the rendering of the content at which no more content associated with the event is available in the LOD buffer.

9. The set top box of claim 6 further comprising an electronic program guide and wherein the processor is further configured to determine that all of the event is not available in the LOD buffer by consulting the electronic program guide to identify a start and end time for the event.

10. At least one non-transitory computer-readable medium encoded with stored instructions which, when executed by a processor, cause the processor to perform steps comprising:

causing content associated with a subsequent portion of an event received from a headend over a content delivery system to be buffered in a live-off-disk (LOD) buffer of a digital video recorder (DVR) device upon receipt, wherein the LOD buffer is configured to buffer content previously received over the content delivery system for rendering during rewind operations;

in response to a request to initiate a rewind operation on the content available in the LOD buffer, rendering the content from the LOD buffer in reverse of normal chronological frame order;

after causing the content to begin being rendered, determining that at least a portion of the content associated with the event is not available in the LOD buffer;

communicating a message, the message specifying a delivery in reverse of normal chronological frame order, and the message comprising a request for the delivery over the content delivery system of additional content associated with at least the portion of the content associated with the event that is not available in the LOD buffer, wherein the portion is an initial portion of the event preceding the subsequent portion of the event; and

upon reaching a point in the rendering of the content during the rewind operation at which no more of the content is available from the LOD buffer, switching the source of the content for rendering from the LOD buffer to the headend,

receiving the delivery as a stream in the DVR device and rendering, without locally storing a file of the requested content received as the stream, and without updating an index file of the requested content, the stream of the additional content of the delivery received in reverse of normal chronological frame order contemporaneously as it is spooled by the headend, the rendering being performed in reverse of normal chronological frame order as received during the rewind operation; and

in response to a second user request, rendering at least a second portion of the additional content received from the content delivery system in normal chronological frame order;

wherein upon reaching a point in the rendering of the content at which the content is available from the LOD buffer, the source of the content for rendering is switchable from the headend to the LOD buffer such that rendering subsequent content associated with the subsequent portion of the event, in normal chronological frame order, is from the LOD buffer.

11. The computer-readable medium of claim 10 wherein requesting receipt of the additional content is performed prior to reaching the point in the rendering of the content during the rewind operation at which no more of the content is available from the LOD buffer.

12. The computer-readable medium of claim 10 , the steps further comprising determining that all of the event is not available in the LOD buffer.

13. The computer-readable medium of claim 10 , the steps further comprising determining that all of the event is not available in the LOD buffer by consulting an electronic program guide to identify a start and end time for the event.