Presentation on theme: "Picture aspect ratio and audio issues on the DTH and DTT platforms Zoltán Vigh Digital Transition Coordinator."— Presentation transcript:
Picture aspect ratio and audio issues on the DTH and DTT platforms Zoltán Vigh Digital Transition Coordinator
Introduction MTVA is a state owned entity with approx employees, to service the public service TV and radio channels: Magyar Televízió and Duna Televízió, as well as Magyar Rádió We purchase, produce, play out and distribute programs for these stations We manage 4 HDTV channels and 8 radio channels. M1 still has an analogue nationwide broadcast network and some programs are mainly for Hungary only M2, Duna and Duna World (TV) are European coverage channels Duna World (TV) and Duna World Radio are for the expat Hungarians living in North- and South-America, and Australia
I found these topics as a problem in the digital transition process HD quality on IPTV after downscaling and upscaling at the home on a Full HD TV set HD to SD scaling quality SD enabling if there is no HD-SD simulcast SD transrating (low quality) on DVB-C and DVB-S networks AFD picture aspect handling (head ends, STBs, TVs) Letterbox SD on a DVB network WSS signal with anamorphic PAL on the analogue network VBI Teletext transmission in the HD world Subtitling on IPTV AAC audio lip-sync issues with low cost STBs Dolby Digital mixdown capability I will show you some details in my presentation
Why HD? After several years of MPEG-2 SD test transmission, the DVB-T MPEG-4 HD broadcasting started in 2008 at Budapest area, with the Beijing Olympic Games. After this successful test, we continued the regular HD broadcasting of the public service channels M1, M2 and Duna The reasons: Today HD is the standard definition (see 4K, UHD) All new studio equipment sold are HD only All new TV sets sold are HD with internal upconversion to match the 1280x720 or 1920x1080 physical resolution of the display The upconversion of the uncompressed SDI to HD-SDI with a broadcast unit is much better in quality than done from a highly compressed MPEG-2 SD signal with a consumer chipset used in the tv set There is a 30%+ penetration of HDTVs in Hungary (approx. 1,4 million HDTV sold) The TV picture size increased from cm to cm, we should serve the viewers
1080i vs 720p We use the 1920x1080i/25 format, to maintain the highest resolution and match the resolution of the new HDTV sets The reasons: We have some HDCAM VTRs in use and these are 1080 only The de-interlace math became very good, so it is easy to make a good quality 1080p or 720p video for the web streaming All the European HD OB Vans are 25i, and we can get the full resolution signal from the international events All the movies are 24P or 25P Most of our programs are progressive style A lot new production equipment are 25/25P only but full HD resolution (Sony CineAlta, DSLR video) The people watch internet video and the progressive frame rate became wear off Due to the restricted capacity of the DVB-T multiplex, we use 1440x1080 On satellite, we use 1920x1080 raster
Digital program distribution of our channels OURSELVES: DVB-S2 (Eutelsat 9A, MHz) Full raster HD, 10 Mbps average bitrate, with AFD picture aspect signaling DVB-T The public service is HD only (except the Duna World, due to limited network capacity), 7 Mbps average bitrate, with AFD picture aspect signaling DVB-S (Eutelsat 9A, MHz) Anamorphic SD (720x576 raster, full raster all time: 4:3 or anamorphic 16:9), with MPEG wide signallng. This will switch off on 31th December 2014 INDEPENDENT TELCO AND CABLE COMPANIES: DVB-C (cable networks), IPTV (cable operators), DVB-S (DTH operators) Anamorphic SD (720x576 raster, full raster all time: 4:3 or anamorphic 16:9), with MPEG wide signaling DVB-C (cable operators), IPTV (cable operators), DVB-S2 (DTH operator) HD (720p, 1440i or 1920i), no AFD picture aspect signaling
No HD and SD simulcast We do not have a HD and SD simulcast on DVB-T for M1, M2 and Duna Reason: No capacity Cost Quality We will not have a HD and SD simulcast on satellite for M1, M2, Duna and Duna World after 2014 Reason: Switch to DVB-S2 and forget DVB-S Cost Quality More flexible capacity management (additional temporary or new channels) To push the migration of the old SD home set top boxes to DVB-S2 and Conax capability for future temporary encryption
Problems with the simulcast-less broadcasting Cable head ends would like to get the MPEG-2 SD transport stream to forward it as is onto their DVB-C networks (cheaper head end) Picture aspect ratio issues (see later) Country specific way, so very few equipment can handle all the requirements Higher cost of the low end set top boxes (no issue anymore, the prices gone down really fast) Education (EuroScart vs. HDMI cable connection) HD logo usage (see later) Slows down a bit the cable providers HD penetration development (they ask money for HD channels – so the free to air HD from us is against their business)
Aspect ratio handling No picture aspect defined in HD standards There are 16:9 AND 4:3 contents time multiplexed in the program (archive 4:3, new 16:9), there is no way to convert the 4:3 content to 16:9, due to quality, composition and copyright issues There is no simulcast (on DVB-T and on DVB-S2 from 2015) – must switch There is a need for picture aspect signaling in HD too, for automatic downscaling to letterbox (for analogue cable networks) or to anamorphic 16:9/4:3 full frame (for digital cable and sat networks) Very few consumer set top box has AFD capability Very few professional cable head end equipment has AFD capability Some tv sets handle the AFD in a wrong method: if they get the 4:3 code then they widen the 4:3 picture to fill the entire screen to save the display against burn in. This is not good and the user can not set the correct 4:3 aspect ration manually in some cases.
What we give to the service providers? For cable and sat operators who get our signal on fiber: We embed WSS onto line 23 of SDI video We embed AFD into HD-SDI video We embed VBI teletext into SDI video We attach stereo and AC3 encoded audio in the SDI signals We maintain time-sync of the video and audio signals For other cable operators, who get our signal from air: We require time-sync from our distributors (Antenna Hungaria, Eutelsat) We specify all the details of our multiplexes. One public service multiplex with 3 HD, 1 SD and 3 radio on DVB-T One LEGACY public service multiplex with 4 MPEG-2 SD (+ picture aspect info) with stereo MPEG-1 audio and TXT and several radio on DVB-S, switch off on the end of 2014 One public service multiplex with 4 MPEG-4 HD (+ AFD) with AC3 and TXT and several AAC high quality radio on DVB-S2
What we require from the cable and DTH operators? Our channels are must carry and we do not have any contract for distribution. Not easy situation. Transmit all part of our signal, including TXT (it’s the law) and all audio channels Do not rescale the signal (720x576 to 544x576, or 1920x1080 to 1280x720) Do not re-encode or transrate our MPEG signal Handle the picture aspect ratio information according to the network Do not crop our 16:9 signal to 4:3, no center-cut enabled. We DO NOT shoot 4:3 safe, the station ID and the PG information are on the 16:9 area, and we place the captions and graphics on the full 16:9 area We ask them to use our HD signals as their source for SD too (better quality) We ask them not to use our SD signals, because it will switch off in 2014 Transmit all of our HD signals if they have a HD package We ask to place our HD signals in the BASIC tier
HD logo on screen if there is no simulcast of SD and HD How to handle the HD logo on screen? NatGeo, Eurosport, History and others has a simulcast and use HD logo on the HD stream. They use HD logo on SD original content too, and this is bad. M1, M2 and Duna does not have an SD simulcast, so the source signal is HD all the time for the analogue and digital cable networks too We mark the original HD content only with the HD logo, not the entire program, but on all platforms (HD and SD). Both are not the perfect solution: some of our viewers believe they watch real HD content on their CRT screen. This is bad. We could not find a good solution yet. If we would not use the HD logo, but our competitors do, then our viewers will say there is no HD on our channels. This is more a marketing issue then technical.
Audio formats we use ON DVB-T We use MPEG-1 Layer II for DVB-T as a primary and legacy stereo format We use Dolby Digital AC3 and a surround format for Hungarian language content (dubbed and original) We will use AAC (standardized for the Hungarian DVB-T network) for original language, but in stereo only (the home theater amplifiers does not handle AAC audio in most cases as a surround format) ON OUR SATELLITE SERVICE We use MPEG-1 Layer II for legacy on DVB-S, both for Hungarian and original language We use Dolby Digital AC3 only with the HD streams on DVB-S2, there is no legacy stereo. We use AAC for radio. The mixdown should be handled by the cable head end IRD or by the home sat receiver. SPECIFICATION!
Lip-sync issue with AAC audio We received some lip-sync issues for other tv channels (RTL, TV2) on the DVB-T network. These tv channels use AAC audio only Some low cost set top boxes used by small analogue cable operators may loose the audio-video sync after hours continues operation. So, there is a need for a reset every 24 hours! This is not a problem with MPEG-1 Layer II, we did not get any feedback on our channels.
Subtitling The subtitling is a must by the Media Law in Hungary, to help the hearing impaired people to watch tv The time-sync is a critical requirement for subtitles On analogue cable the only widely used method is the TELETEXT We have one common teletext signal for our four channels, and we use four pages (111, 222, 333, 444) for the channel specific subtitles The TELETEXT is not impemented in HD-SDI signal format, so we should provide a time-synced SD downconverted version of the video in SDI format This SDI video with embedded teletext data then became encoded to MPEG- 2 and the teletext stream will be used by the multiplexer. The timing is critical (MPEG-2 SD and MPEG-4 HD encoding time is different). The digital cable and SAT operators can transcode the teletext subtitles to DVB-SUB format to use in their own networks There is not teletext on IPTV, the operators without their own subtitle method have legal problems