Methods and systems for displaying interlaced video on non-interlaced monitors

• US 6,359,654 B1
• Filed: 02/12/1997
• Issued: 03/19/2002
• Est. Priority Date: 02/14/1996
• Status: Expired due to Term

• Current Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Original Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Inventors: Felts, III, Benjamin Edwin, Brunolli, Michael J., Wilson, David A. G., Glennon, Stephen G.
• Primary Examiner(s): Faile, Andrew
• Assistant Examiner(s): Srivastava, Vivek
• Application Number:
  US08/798,240
• Time in Patent Office: 1,861 Days
• Field of Search: H07/N.701, H07/N 1.120, H07/N.720, 348/448, 348/449, 348/454, 348/455, 348/456, 348/458, 348/459, 348/446, 348/445, 348/443, 348/441, 348/558, 348/556, 348/555, 348/543, 348/544, 348/545, 348/546, 348/576
• US Class Current: 348/448
• CPC Class Codes: G09G 2310/0229 De-interlacing
• CPC Class Codes: G09G 5/00 Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators image data processing or generation, in general G06T
• CPC Class Codes: H04N 7/012 Conversion between an interlaced and a progressive signal for graphics images G09G2310/0229

Abstract

A number of methods to display interlaced video on non-interlaced monitor are disclosed. One method is to display all of the incoming fields but one at a time, and correcting for the positional offset of one field relative to another in the interlaced data. An important aspect of the present invention is the correction of the positional offset of the two interlaced video fields. There are two ways presented to deal with the vertical offset of the two fields in accordance with the present invention. The first way is that the two fields can be displayed at different positions on the display using a non-interlaced display. The second way is that the video data can be altered to correct the positional offset between the fields. Another method of the present invention is to lock the frame rate of the output video to the incoming field rate or a multiple of the incoming field rate, or to certain sub-multiples of the incoming field rate. An important feature of this method is that each frame of the output monitor need not match the incoming field time precisely. As long as each output frame is displayed exactly the predetermined number of times, the appearance of smooth motion will be maintained.

Claims

1. A method for displaying interlaced video data on a non-interlaced monitor, the interlaced video data comprising a plurality of paired fields, each pair of fields being vertically offset relative to each other by one-half of a field line spacing distance, each field comprising a plurality of lines of video data, the method including:

(a) capturing a first field and a second field of each pair of fields into respective buffers;

(b) scaling each of the first field and second field of each pair of fields to fill vertical resolution of the non-interlaced monitor;

(c) adjusting one of the first field or second field of the pair of fields to substantially correct for the vertical offset between the pairs of fields, where said adjusting is performed concurrently with said scaling;

(d) displaying the first field of each pair of fields on the non-interlaced monitor in a first time period; and

(e) displaying the second field of each pair of fields on the non-interlaced monitor in a second time period subsequent to the first time period.

2. The method of claim 1, wherein scaling is achieved by line replication.

3. The method of claim 1, wherein scaling is achieved by line dropping.

4. The method of claim 1, wherein scaling is achieved by vertical interpolation between at least adjacent lines in the field being scaled.

5. The method claim 1, wherein the scaling step includes scaling to a size other than two times the size of the interlaced video data by interpolating the video data.

6. The method of claim 1, wherein the step of scaling is performed before the step of adjusting.

7. The method of claim 1, wherein the step of scaling is performed after the step of adjusting.

8. The method of claim 1, wherein the adjusting step includes changing display positions of one of the scaled first field or scaled second field by one or more lines on the noninterlaced monitor.

9. The method of claim 1, wherein the adjusting step is achieved by vertical interpolation between at least adjacent lines in the field being adjusted.

10. A method for displaying interlaced video data on a non-interlaced monitor, the interlaced video data comprising a plurality of paired fields and having a field rate, each field comprising a plurality of lines of video data, the non-interlaced monitor having a variable frame display rate and a maximum frame display rate, the method including:

(a) capturing a first field and a second field of each pair of fields into distinct respective buffers at the interlaced video data field rate;

(b) scaling each of the first field and second field of each pair of fields to fill vertical resolution of the non-interlaced monitor;

(c) adjusting one of the first field or second field of the pair of fields to substantially correct for the vertical offset between the pairs of fields;

(d) setting the frame display rate of the non-interlaced monitor to a multiple of the field rate of the interlaced video data, such that the set frame display rate is no greater than the maximum frame display rate of the non-interlaced monitor;

(e) locking the first field and the second field of each pair of fields to the set frame display rate, where said locking includes determining a difference in field rate of the interlaced video data and the set frame display rate of the displayed first field and second field by sampling an input line counter and an output line counter; and

(f) sequentially displaying the first field and the second field on the non-interlaced monitor at the set frame display rate, such that each of the first field and second field are displayed for a predetermined number of frame times of the non-interlaced monitor.

11. The method of claim 10, wherein the set frame display rate is a sub-multiple of the field rate of the interlaced video data.

12. The method of claim 10, wherein the set frame display rate is a multiple of the field rate of the interlaced video data.

13. The method of claim 10, wherein the locking step includes the step of adding or removing one or more lines in a vertical blanking region of the interlaced video data.

14. The method of claim 10, wherein the locking step includes the step of increasing or decreasing the length of one or more lines in a vertical blanking region of the interlaced video data.

15. The method of claim 10, wherein the locking step includes the step of adjusting the frequency of a clock used to generate the set frame display rate.

16. The method of claim 10, wherein the locking step includes sensing drift in relative positions between lines in the interlaced video data and the displayed first field and second field.

17. The method of claim 10, wherein said locking includes determining a difference in field rate of the interlaced video data and the set frame display rate of the displayed first field and second field by use of a difference counter.

18. A method for displaying interlaced video data on a non-interlaced monitor, the interlaced video data comprising a plurality of paired fields and having a field rate, each field comprising a plurality of lines of video data, the non-interlaced monitor having a variable frame display rate and a maximum frame display rate, the method including:

(a) capturing a first field and a second field of each pair of fields into distinct respective buffers at the interlaced video data field rate;

(b) scaling each of the first field and second field of each pair of fields to fill vertical resolution of the non-interlaced monitor;

(c) adjusting one of the first field or second field of the pair of fields to substantially correct for the vertical offset between the pairs of fields;

(d) setting the frame display rate of the non-interlaced monitor to a multiple of the field rate of the interlaced video data, such that the set frame display rate is no greater than the maximum frame display rate of the non-interlaced monitor;

(e) locking the first field and the second field of each pair of fields to the set frame display rate, where said locking includes determining a difference in the field rate of the interlaced video data and the set frame display rate of the displayed first field and second field by sampling a line video position within at least one of the first field and second field at a consistent time in an output monitor display cycle; and

(f) sequentially displaying the first field and the second field on the non-interlaced monitor at the set frame display rate, such that each of the first field and second field are displayed for a predetermined number of frame times of the non-interlaced monitor.