JPS6226106B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a storage method in PCM (Pulse Code Modulation).

PCM is the coding of an analog signal such as an acoustic signal into a digital signal consisting of "0" and "1".When an acoustic signal is encoded in this way and transmitted or stored, it becomes Since it is not directly affected by distortion generated inside the device or noise mixed in, it is possible to obtain a large dynamic range over a wide band, and when applied to a recording/playback device, it is possible to eliminate rotational irregularities generated from the rotation mechanism. Even minute vibrations are not a problem, making it possible to record and playback with extremely high fidelity.

On the other hand, since PCM handles an extremely large amount of information, existing fixed single-head tape recorders are useless. Therefore, there are two types: one uses a fixed multi-head, and the other uses a rotating head, which is the same as existing VTRs.

The present invention relates to the latter, ie, a rotating head storage system.

Figure 1 shows an outline of a PCM system using a rotating head system. An analog signal A from a sound source 1 is sampled by a sampling circuit 2 using sampling pulses of an appropriate period to become a staircase wave signal B, and the staircase wave signal B is converted into a digital signal by an AD conversion circuit 3. The digital signal C is guided to a recording storage circuit 4 which converts it into a television signal for recording on a magnetic tape by a VTR 5, and from this storage circuit 4 it is converted into a television signal.
PCM code D is output, and this code signal D is
Recorded on magnetic tape using VTR5.

Next, it was recorded on magnetic tape in this way.
The case of reproducing a PCM code D signal will be explained. By operating VTR5 in playback mode,
A PCM code E in the form of a television signal is obtained from the VTR 5, and this code signal E is led to a reproduction storage circuit 6 where it is returned from the television signal to a digital signal F. The digital signal F is converted into a staircase wave signal G by a DA conversion circuit 7. Furthermore, the demodulated staircase wave signal G is restored to an analog signal H by a restoration circuit 8, and then sent to a speaker 9.
is played as audio.

The present invention provides a storage system for writing and reading digital data into and from the recording and storage circuit 4 used in such a PCM system.

Generally, in PCM, interleaving is applied to prevent data from being continuously dropped. Also,
In a system using a VTR, a buffer memory with a predetermined storage capacity, that is, a recording storage circuit, is used to faithfully record the data sampled during the V sync signal period of the VTR recording medium and the head switching period. 4 is provided. To explain with specific numbers, 1V of a VTR TV signal is
262.5H, but 17.5H is used to remove unstable factors before and after head switching. Therefore, 262.5−17.5=245(H) That is, it is necessary to record all data sampled during 262.5H in 245H, and to compress this data, the digital signal from the AD conversion circuit 3 is temporarily stored. However, a recording/memory circuit 4 is required which reads out the amount of data corresponding to the V period in a period excluding the V synchronization period and the head switching period. On the other hand, in this memory circuit 4, the sampling circuit 2 samples 2.8 times during the 1H period, so in the 17.5H period, there are 2.8 x 17.5 = 49 (samples), that is, 49 samples, and since it is usually stereo in PCM. , R, and L channels, and one frame consists of three samples, so 98 ÷ 3 ≒ 33 (samples), that is, each data is stored with an interval of at least 33 addresses. It is necessary to do so. In the present invention, each data is stored at intervals of 40 addresses for reasons of safety and circuit design.

On the other hand, although the data interval for interleaving as described above is arbitrary, it has been found from experimental data that most data dropouts can be compensated for with an interval of 10 data. 16 data intervals are used.

Based on this address interval and interleave interval, the state of writing data to the recording storage circuit 4 will be explained with reference to FIG. The data arriving from the AD conversion circuit 3 is real-time data, and the data is "L ₀ , R ₀ , L ₁ , R ₁ , L ₂ , R ₂ , P ₀ ".
It consists of the form of L ₀ , L ₁ , L ₂ are the 0, 1, and 2nd data of the left channel, R ₀ , R ₁ , R ₂ ,
indicates the 0, 1, and 2nd data of the right channel, and P ₀ indicates the parity code. In the present invention, if this data "L ₀ " is stored at address 0 of the storage circuit 4, the next data "R ₀ " is 40
"L ₁ " is written to address 96, "R ₁ " is written to
The addresses are specified so that "L ₂ " is written at address 256, "R ₂ " is written at address 360, and "P ₀ " is written at address 480. That is, the data format of the 1H period coming from the AD conversion circuit 3 is "L _3n+
0 , R _3n+0 , L _3n+1 , R _3n+1 , L _3n+2 , R _3n+2 , P _3
n '', this L _3n+0 is set to the address ``m'', R <sub>3n+0</sub> is set to the address ``L _3n+0 is written to +B'' (that is, address m+B), and L _3n+1 is set to the address ``M''. Address to write R _3n+0 +(B+D×
1)", write R _3n+1 to the address "L _3n+1 + (B+D×
2)", write L _3n+2 to the address "R _3n+1" + (B+D×
3)", write R _3n+2 to the address "L _3n+2 + (B+D×
4)", write P _3n to the address "R _3n+2 + (B + D ×
5)", the address is specified to be written.
Here, m is an integer (...-1, 0, 1, 2...), B
is the buffer address interval, and D is the interleaving interval. Therefore, each address 40, 96, 168, 256,
The origin of 360 and 480 is as follows, assuming m=0, B=40, and D=16.

40=0+40 96=40+40+16×1 168=96+40+16×2 256=168+40+16×3 360=256+40+16×4 480=360+40+16×5 This series of data “L ₀ , R ₀ , L ₁ , R ₁ , L ₂ ,
The data following “R ₂ , P ₀ ”, that is, “L ₃ ,
R ₃ , L ₄ , R ₄ , L ₅ , R ₅ , P ₃ ” are for each address, namely 1, 41, 57, 97,
It is written to addresses 169, 257, 361, and 481 in order.

Note that this recording memory circuit 4 is the highest in this embodiment.
It has 511 addresses, and when data is written to this 511 address, a cyclic address system is adopted in which the next data is written back to address 0.

On the other hand, data written in the recording storage circuit 4 is read out as follows. That is, first, the contents stored at address 0 are read out, then the contents at address 24 are read out, and thereafter the contents at addresses 64, 120, 192, 280, and 384 are read out in sequence. Each of these read addresses has the following relationship.

0 = Real time reading 24 = 40-16 x 1 64 = 96-16 x 2 120 = 168-16 x 3 192 = 256-16 x 4 280 = 360-16 x 5 384 = 480-16 x 6 Each of these readings At addresses 0, 24,..., 384,
Among the series of data, L ₀ , R _-48 , L _-95 , R _-143 ,
L _-190 , R _-238 and P _-288 are each stored in advance,
These data “L ₀ , R _-48 , L _-96 , R _-143 ,
L _-190 , R _-239 , P _-288 '' are sequentially read out from the recording memory circuit 4, and these seven pieces of data are the television signal.
The 1H period signal is sent to the VTR 5, and the PCM coded audio signal is recorded in the form of a television signal.

For reference, a comparison between real-time data and recorded data actually recorded by the VTR 5 is shown in FIG. In Fig. 3, A is real-time data and B is recorded data, and there is the following relationship between these two data.

L ₀ = L ₀ R _-48 = R _0-16×3×1 L _-95 = L _1-16×3×2 R _-143 = R _1-16×3×3 L _-190 = L _{2-16× 3×4} R _-238 = R _2-16×3×5 P _-288 = P _0-16×3×6 “16” used in these relational expressions is the interleave interval, and “3” is 1 This is the number of data for each channel in the frame, and "1 to 6" indicates a multiple for sequentially expanding each data interval.

It should be noted that once the contents of address 511, which is the final address of this recording storage circuit 4, are read out, the next step returns to address 0, as in the case of writing.

As explained above, the recording storage circuit 4 stores real-time data, at least the VTR 5 recording medium.
During the synchronization signal period and the head switching period, data sampled by the sampling circuit 2 is written at addresses having the number of addresses that can be stored, and from this recording storage circuit 4, the above real-time data is written at locations. The recorded data row is reconstructed by extracting the instantaneous data from addresses that are younger than the written address by the interlib interval.

In this way, real-time data is sequentially written in the recording storage circuit 4 in a scattered manner, and at the same time, it is extracted and read out sequentially from a location separated by the interleaving interval from the writing location, and the stored contents are constantly being refreshed.

Next, the case where data is read from the VTR 5 and an audio signal is obtained from the data will be explained with reference to FIG. As mentioned above, the data recorded on the VTR 5 is interleaved to protect against data dropout, etc., and the reproduced data from the VTR 5 cannot be treated as an audio signal as is. This playback data also includes jitter during recording and playback of the VTR5, so it must be compensated for. Therefore, a reproduction storage circuit 6 is required that temporarily stores the reproduction data from the VTR 5, reads it out at a speed different from this storage speed, and returns it to real-time data. First, the state of writing reproduction data into the reproduction storage circuit 6 will be explained.

As explained earlier, the read data read from the VTR 5 is "L ₀ , R _-48 , L _-95 , R _-143 ,
L _-190 , R _-238 , P _-288 '', and among this series of data, "L ₀ " is written to address 0 of the reproduction storage circuit 6, "R _-48 " is written to address 144, and "L _{- 95} '' is written and memorized at address 272, ``R <sub>-143</sub> '' at address 384, ``L _-190 '' at address 480, ``R <sub>-238</sub> '' at address 560, and ``P _-288 '' at address 624. The address is specified so that the That is, the data format for one frame period read from the VTR 5 is "L _3n , R _3n-3×
D , L _3n-3×2D+1 , R _3n-3×3D×1 , L _3n-4D+2 , R _3n-3
×5D+2 , P _3n-3×6D ”, this L _3n is expressed as the address “m”, and R _3n-3×D is expressed as the address “L _3n is written + (B + D
×5)”, write L _3n-3×2D+1 to the address “R _3n-3×D +
(B+D×4)”, write R _3n-3×3D+1 to the address “L _3n-3×2D+1 +
(B+D×3)”, write L _3n-3×4D+2 as the address “R _3n-3×3D+1 +
(B+D×2)”, write R _3n-3×5D×2 as the address “L _{3n-3×4D+2”} +
(B+D×1)”, write P _3n-3×6D as the address “R _{3n-3×5D+2”} +
(B+D×0)”. Here, m is an integer (...-1, 0, 1, 2
), B is the number of memory addresses for absorbing jitter in the VTR5, in other words, the memory address for time axis conversion, and D is for restoring the interleaved data that was written when writing in the VTR5. This is the number of memory addresses for Therefore, the origin of the settings of these memory addresses 144, 272, 384, 480, 560, and 624 is as follows, assuming m=0, B=64, and D=16.

144=64+16×5 272=144+64+16×4 384=272+64+16×3 480=384+64+16×2 560=480+64+16×1 624=560+64+16×0 64 of the constants used in these calculation formulas
is the number of memory addresses for absorbing jitter in the VTR5, in other words, it is the memory for time axis conversion, and 16 is the memory for restoring the interleaved data written when writing in the VTR5. In terms of the number of addresses, the interval between write addresses becomes narrower.

After this one frame of data, the data read out from the VTR 5 are “L ₃ , R _-45 , L _-92 ,
"R _-140 , L _-187 , R _-235 , P _-285 " are respectively stored at addresses one address larger than the previous data. As is clear from FIG. 4, the same applies to the data of the next frame.

The data written in the reproduction storage circuit 6 in this manner is read out and restored to real-time data in the following manner. The contents of address 0 are read first, the second is address 160, the third is address 304, and the third is address 4.
No. 432, No. 544, No. 640.
The contents of address 720 are read out at the seventh address. At each of these addresses, follow the procedure described above to create a VTR5.
The information from is pre-written, but
The respective written contents are L ₀ , R ₀ , L ₁ , R ₁ ,
L ₂ , R ₂ , and P ₀ , and real-time data is restored by sequentially reading out the contents of these addresses.

The read address of the reproduction storage circuit 6 is set as follows. Regardless of the first address 0 to be read, the second address 160 is the second write address, which is address 144 plus the interleave interval of 16, and the third address 304 is the third write address 272. The address is the address plus twice the interleave interval 32. Similarly, the address obtained by adding a multiple of the interleave interval to each write address corresponds to each write address. When the reading from address 720 is completed, the next reading address plus 1, that is, 1, 161, 305, 433, 545, 641, 721,
Data is read out in order from each address,
The read contents are L ₃ , R ₃ , L ₄ , R ₄ , L ₅ ,
R ₅ and P ₃ become the next real-time data.

The storage capacity of the reproducing memory circuit 6 is 1024 addresses, and a cyclic address system is adopted in which address 0 is accessed after address 1023.

In the above description, we have explained the operation of writing and reading data to and from the recording memory circuit 4 and the reproduction memory circuit 6.As shown in FIG. Write address circuits 11, 12 and read address circuits 13, 14 are associated with each other, and address signals as described above are emitted from each of these address circuits 11, 12, 13, 14, and based on each address signal, Writing and reading are performed using

As is clear from the above description, the present invention is applicable to VTR
In a PCM using a VTR, the digital signal from the AD conversion circuit is temporarily stored, and the amount of data corresponding to the V period is read out during a period excluding the V synchronization period and head switching period to create digital data to be written to the VTR. The digital signal is recorded at a distance corresponding to a multiple of the interleaving interval and an interval capable of storing the digital signal arriving during the V synchronization signal period and the head switching period with respect to the storage circuit. At the same time, the data is sequentially read out from the addresses that are younger by a multiple of the interleaving interval for each write address in the recording/memory circuit, so the read data includes the data of the V synchronization signal period and the head switching period. It also compresses and includes interleaving to compensate for data loss, making it extremely useful for PCM using a VTR. Furthermore, according to the storage method of the present invention, the storage capacity of the recording storage circuit can be minimized, and therefore, a buffer memory with a small storage capacity can be used as the recording storage circuit. have

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an outline of a PCM system using a VTR, Fig. 2 is a diagram of the storage contents of the recording storage circuit according to the present invention, and Fig. 3 shows the combination of real-time data and read data from the recording storage circuit. Comparison chart, 4th
The figure is a memory content diagram of the reproduction memory circuit, and Figure 5 is a block diagram of the peripheral circuits of each memory circuit, where 1 is a sound source, 2 is a sampling circuit, 3 is an AD conversion circuit, 4 is a recording memory circuit, and 5 is a block diagram of the peripheral circuits of each memory circuit. VTR, 6 is a playback storage circuit, 7 is a DA conversion circuit, 8 is a restoration circuit,
9 indicates a speaker, and 11, 12, 13, and 14 address circuits, respectively.

Claims (1)

[Claims] 1. A PCM that digitizes and records two-channel audio signals includes an AD conversion circuit that digitizes an analog signal from a sound source, and a temporary storage of the digital signal from the AD conversion circuit. Shiso V
A recording memory circuit that reads an amount of data corresponding to a period excluding a V synchronization period and a head switching period, a VTR that records compressed and interleaved data using the recording memory circuit, and
A playback storage circuit that converts data played back by a VTR into real-time data, a DA conversion circuit that converts digital signals read from the playback storage circuit into analog signals, and a speaker that produces audio signals output from the DA conversion circuit. and an address corresponding to a multiple of the interval B and the interleave interval D, at least for the recording and storage circuit to be able to store digital signals that arrive during the V sync signal period and head switching period in the VTR. In order to sequentially write the digital signals from the AD conversion circuits at intervals of 1H, the data of 1H period coming from the AD conversion circuits are written as "L _An+0 , R _An+0 , L _An+
1 , R _An+1 , ... L _An+(A-1) , R _An+(A-1) ", L _An+0 is the address "m", R _An+0 is the address "L _An+ Write L _{An+1 to} the address "R _An+0 is written to the address + (B+D
×1)”, write R _An+1 to the address “L _An+1 + (B+D
×2)", 〓 R _An+(A-1) to "L _An+(A-1) address + {B
+D×2×(A-1)}” (where A is the number of data for one channel in 1H period, m is an integer), and write to each of the above write addresses of the recording storage circuit. On the other hand, this storage method is characterized in that data is sequentially read from addresses that are a multiple of the interleave interval to obtain compressed and interleaved digital data.