Design considerations of the video compression system of the new DV camcorder standard Citation for published version (APA): With, de, P. H. N., & Rijckaert, A. M. A. (1997). Design considerations of the video compression system of the new DV camcorder standard. IEEE Transactions on Consumer Electronics, 43(4), 1160-1179. https://doi.org/10.1109/30.642384 DOI: 10.1109/30.642384 Document status and date: Published: 01/01/1997 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. 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If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policy If you believe that this document breaches copyright please contact us at: [email protected] providing details and we will investigate your claim. Download date: 27. Sep. 2021 1160 IEEE Transactions on Consumer Electronics, Vol. 43, No. 4, NOVEMBER 1997 NSlDERATlONS OF THE VID COMPRESSION SYSTEM OF THE NEW DV CAMCORDER STANDARD P. H. N. de With, member IEEE, A. M. A. Rijckaert Philips Research Labs., Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands Abstract - The digital camcorder sys- Scanner 2 heads tem DV, which features advanced intra- Scanner diameter 21.7 mm frame DCT-based video compression, has Scanner speed 9000 rpm been successfully introduced for the con- Tape width 6.35 mm Tape thickness 7 Pm sumer and semi-professional user. This pa- Track pitch 10pm per focuses on the design considerations Recording rate 41.85 Mbit/s and system issues that have resulted in the Tracking Embedded tracking tones final video compression standard applied. Channel modulation 24-25 code Keywords: DV, digital video, camcorder, video Error correction code R-S product code Video bit rate 25 Mbit/s compression, recording, DCT. Video coding 8x8 intraframe DCT Trick mode implementation Video macroblock shuffling 1. Introduction Table 1: Key parameters of digital consumer DV Recently, advanced video compression has be- recorder. come an emerging and enabling technology for new systems in digital transmission and storage. been further developed by a substantial group of An example of successful video compression sup- companies. The main issue of the standard was porting digital video broadcasting is the MPEG to introduce attractive small camcorder products standard [l],which is widely used in other envir- in the mid-nineties. Since September 1995, a onments as well. number of companies have introduced DV cam- In this paper, we describe digital home-use corders into the market. The small products recording of high-quality video signals, which is provide good examples of the original intentions relevant as a high-performance successor of the and aims of the standardization group. Based existing analogue formats (Hi-8 and VHS). We on the DV technology, the professional systems will particularly focus on the video compression DVCPRO and DVCAM have emerged, which are system and its relation to the adopted record- increasingly popular. ing system parameters, thereby giving technical Despite the acceptance of the MPEG and insight to the design considerations of this com- JPEG standards in numerous applications, the pletely new recording standard. The technical development of the DV video compression stand- insight results from continuous participation in ard was largely guided and justified by the tar- the standardization committees for DV record- getted product and cassette size, power consump- ing and video compression for a number of years. tion and the consumer price level. Irrespective of For consumer recording, the trend is towards the previous issues, a number of recording system small recording mechanics, especially for port- constraints have to be satisfied in any case and able applications, and digital recording of com- are rather typical, namely pressed digital video signals. These aspects have - editing, preferably on picture basis; been combined into the DV system, which was - robust for repeated (de-)compression, firstly announced in 1993 [2] and which has resulting from analogue video dubbing; Manuscript received August 1, 1997 0098 3063/97 $10.00 1997 IEEE de With and Rijckaert: Design Considerations of the Video Compression System of the New DV Camcorder Standard 1161 format 4 - - Source Icoding video in recording F‘ - - ! - - mechanics ____ I Channel T audio, data .-, I Coding I I vert. 25-24 L_-- ______ w t ECC , decod tracking video out I Figure 1: Block diagram of complete processing of consumer DV recording system. 2. System architecture Figure 1 portrays the block diagram of the re- cording system. Signal processing is divided into two main classes: recovered data bursts in trick play tape - source coding employing video compression and source data formatting, Figure 2: Multi-track format and trick play. - channel coding using error-correcting codes and modulation codes for spectrum shaping of the bit stream. - multitrack format, using a set of The video compression is based on the Dis- tracks for one frame (see Fig. 2); crete Cosine Transform (DCT), and subsequent - forward and backward search on tape, quantization and Variable-Length Coding (VLC) from small data bursts pictures of the transformed video data. Since the opera- have to be recovered (see Fig. 2); tions are performed on blocks of 8 x 8 samples, - very high robustness; the video input signal is stored for line-to-block - high picture quality. conversion. Shuffling of data blocks is performed for improving the picture quality under normal and trick play. The satmpling of the video signal Section 2 presents briefly the architecture of is derived from the CCIR-601 standard (4:2:2) the DV recording system. Section 3 discusses the with 13.5 MHz sampling frequency for the lumin- starting point of the standard: the cassette size. ance (Y) signal. The colour-difference signals (Cr In Section 4 we address the options for the drum and Cb) are subsampled either horizontally with parameters, such as speed and size, given the dif- a factor 2 (4:l:l) for 60 Hz or vertically with a ference between 50 and 60 Hz video field rates factor 2 (4:2:0) for 50 Hz systems. and taking into account various operation modes For Error-Correction Coding (ECC), the DV of the recorder. Section 5 analyzes the conditions recording format employs the obligatory Reed- during trick play and in particular for high-speed Solomon (R-s) product codes, of which the error- search. We derive the best data packet length for correcting properties $aredefined within a track. the recording channel. In Section 6, video com- After compression, the data are organized in pression features are elaborated into detail and small packets, called sync blocks. Each sync the individual coding steps (DCT, Q, VLC) will block gets some parity bytes (HECC) assigned be described. In Section 7 we discuss a special to it for random byte errors and for error detec- video data shuffling technique to improve the per- tion of burst errors. Subsequently, the complete ceptual performance of the recorder during the video data block (or a.udio) is extended with ex- trick-play modes. 1162 IEEE Transactions on Consumer Electronics, Vol. 43, No. 4, NOVEMBER 1997 I I I- -t At=L w Ab- b Tp C=AtlAb Figure 4: Important 8mm tape parameters. Figure 3: Cassette parameters and corresponding tape length of the 8mm standard. Topic Estim. fraction Channel Modulation 4 Yo 5.4 tra sync blocks containing vertical partity bytes Tracking information 0 Yo 1.8 (VECC). The performance of these codes is very Synchronisation + Identification 4 % 6.5 Two-dim. Error Correction 15 % 20.3 good for removing random errors and general Digital Audio 6 % 5.2 burst errors. As a second step in channel cod- Auxiliary data 2 % 2.2 ing, a high-efficiency DC-free 24-25 channel code Subcode information 2 % 1.2 1 % was adopted, described in [3] [4], to constitute Margins at track begidend 3 % (1.2) Edit gaps and pre/post-amble 3 % 9.1 7 %a pilot tones for tracking which are embedded in I Video I 61 % 11 83.2 I 62%I the data. The recording mechanism is based on a small Total one track 100% 134.9 100% drum of 21.7 mm which rotates at 9000 rpm. The basic recording mode (2 x 1 head) has a capa- Table 2: Contributions to recording rate. city of 41.85 Mbit/s (equiv. to 25 Mbit/s video), but the system can be upgraded mechanically and electronically to 83.7 Mbit/s (50 Mbit/s net audio (221 O wrap) equals 6.6 mm, which is some- video rate) for HDTV recording.