Multi-channel video pump
View Patent ↗A system for streaming a plurality of video or other recorded signals from storage to receiving devices maintains each of the signal streams at their encoded bit rate. The bit rate of each stream is detected from the stored signals and a corresponding queue is set up in memory or in a network interface card for outputting data at the detected bit rate. A channel timing module in the signal streaming device contains a two-stage dithered counter for each bit rate. The first stage of the counter counts one clock cycle longer than the second stage. By adjusting the ratio of the first stage and second stage counters in a fixed number of cycles (the dither cycle) a very precise average count is achieved. The average count is calculated to achieve the desired bit rate with a given packet size. Every time either the first stage of the second counter times out, a packet of data is sent to the corresponding queue in the network interface. As a result, the network interface is able to output packet isochronous signals with an average bit rate within one bit per second of desired bit rates between one megabit/second and 20 megabit/second and with a jitter of less than two milliseconds.
1. An apparatus to output multiple streams of stored signals, each stream encoded at one of a plurality of bit rates and read from recordings, comprising:
a streaming device to detect which of the bit rates is used to encode each respective stream of the stored signals on the recording and to output each stream as packet isochronous signals at the one of the bit rates for that respective stream, wherein the streaming device outputs each stream of the packet isochronous signals with an average bit rate within one bit per second of the one of the bit rates used to encode that respective stream.
2. An apparatus as recited in claim 1 , wherein said streaming device outputs each stream of the packet isochronous signals with a jitter of less than two milliseconds.
3. An apparatus as recited in claim 1 , wherein said streaming device comprises a plurality of timer circuits, each including
a base counter to count a truncated period for transmission of packets; and
a dithering circuit to indicate transmission of one of the packets one clock pulse later than the truncated period, a predetermined number of times within a dither cycle.
4. An apparatus for simultaneously reproducing multiple recordings from storage devices for transport on a network, comprising:
buffers to receive stored signals from the multiple recordings, each recording containing stored signals encoded at one of a plurality of bit rates;
a control unit, coupled to said storage devices, to receive requests to reproduce the multiplied recordings and to control playback of the stored signals by the storage devices;
a real-time pump, coupled to said buffers and said control unit, to detect which of the bit rates is used to encode the stored signals on each of the respective multiple recordings and to output sport stream packets, each transport stream packet based on the stored signals from one of the multiple recordings;
a network interface, coupled to said control unit and said real-time pump, to receive the transport stream packets in corresponding queues and to output over the network multiplexed packet isochronous signals corresponding to the stored signals on the multiple recordings requested to be reproduced, each stream of the packet isochronous signals on the network having an average bit rate of the one of the bit rates used to encode the stored signals corresponding thereto; and
a channel timing module, coupled to said real-time pump, to control timing of output of the transport stream packets, wherein said channel timing module comprises a plurality of two-stage counters and channel status logic units corresponding to said two-stage counters.
5. An apparatus as recited in claim 4 , wherein said network interface outputs each stream of the packet isochronous signals with the average bit rate within one bit per second of the one of the bit rates used to encode the stored signals corresponding thereto.
6. An apparatus as recited in claim 4 , wherein said network interface outputs each stream of the packet isochronous signals with a jitter of less than two milliseconds.
7. An apparatus as recited in claim 4 , wherein each two-stage counter corresponds to one of the plurality of bit rates.
8. An apparatus as recited in claim 4 , wherein at least one of the two-stage counters further comprises:
a base counter to count a truncated period for mission of packets; and
a dithering circuit to indicate transmission of the transport stream packets within a corresponding stream one clock pulse later than the truncated period, a predetermined number of times within a dither cycle.
9. A system for transmitting multiple streams of stored signals to receiving devices, comprising:
at least one playback device to access recordings, each recording containing stored signal encoded at one of a plurality of bit rates;
a streaming device, coupled to said at least one playback device, to receive requests to reproduce specified recordings, to detect the one of the bit rates used to encode the stored signals on each of the specified recordings, and to output a stream of packet isochronous signals based on the stored signals of the specified recordings at the one of the bit rates for each of the specified recordings, wherein said streaming device outputs each stream of the packet isochronous signals with an average bit rate within one bit per second of the one of the bit rates at which the corresponding recording was encoded; and
a network, coupled to said streaming device and the receiving devices, to deliver each stream of the packet isochronous signals to the receiving devices.
10. A system as recited in claim 9 , wherein said streaming device outputs each stream of the packet isochronous signals with a jitter of less than two milliseconds.
11. A system as recited in claim 9 , wherein said streaming device comprises a plurality of timer circuits, each including:
a base counter to count a truncated period for transmission of packets; and
a dithering circuit to indicate transmission of one of the packets one clock pulse later than the truncated period, a predetermined number of times within a dither cycle.
12. A method of transmitting multiple streams of stored signals to receiving devices, comprising:
reading the stored signal from recordings, each recording encoded at one of a plurality of bit rates;
detecting the one of the bit rates used to encode the stored signals for each respective stream; and
outputting to the receiving devices each stream of stored signals as packet isochronous signal at the one of the bit rates for that respective stream, wherein each stream of the packet isochronous signals is outputted with the average bit rate within one bit per second of the one of the bit rates used to encode that respective stream.
13. A method as recited in claim 12 , wherein said outputting outputs each stream of the packet isochronous signals with a jitter of less than two milliseconds.
14. A method as recited in claim 12 , wherein said outputting of each packet of isochronous signals occurs on a timing pulse produced from clock pulses generated at a clock rate, the timing pulse produced with an average period of greater precision than the clock rate.
15. A method as recited in claim 13 , further comprising producing timing pulses by
counting the clock pulses for a truncated period based on the average period; and
generating the timing pulses one clock pulse later than the truncated period, a predetermined number of times within a dither cycle.