Tag Archives: video

Media Recognition: DV part 3

DVCAM (encoding)

Type:
Digital videotape cassette encoding
Introduced:
1996
Active:
Yes, but few new camcorders are being produced.
Cessation:
Capacity:
184 minutes (large), 40 minutes (MiniDV).
Compatibility:
DVCAM is an enhancement of the widely adopted DV format, and uses the same encoding.
Cassettes recorded in DVCAM format can be played back in DVCAM VTRs (Video Tape Recorders), newer DV VTRs (made after the introduction of DVCAM), and DVCPRO VTRs, as long as the correct settings are specified (this resamples the signal to 4:1:1). DVCAM can also be played back in compatible HDV players.
Users:
Professional / Industrial.
File Systems:
Common Manufacturers:
Sony, Ikegami.
DVCAM is Sony’s enhancement of the DV format for the professional market. DVCAM uses the same encoding as DV, although it records ‘locked’ rather than ‘unlocked’ audio. It also differs from DV as it has a track width of 15 microns and a tape speed of 28.215 mm/sec to make it more robust. Any DV cassette can contain DVCAM format video, but some are sold with DVCAM branding on them.
Recognition
DVCAM labelled cassettes come in large (125.1 x 78 x 14.6 mm) or MiniDV (66 x 48 x 12.2mm) sizes. Tape width is ¼”. Large cassettes are used in editing and recording decks, while the smaller cassettes are used in camcorders. They are marked with the DVCAM logo, usually in the upper-right hand corner.

HDV (encoding)

Type:
Digital videotape cassette encoding
Introduced:
2003
Active:
Yes, although industry experts do not expect many new HDV products.
Cessation:
Capacity:
1 hour (MiniDV), up to 4.5 hours (large)
Compatibility:
Video is recorded in the popular MPEG-2 video format. Files can be transferred to computers without loss of quality using an IEEE 1394 connection.
There are two types of HDV, HDV 720p and HDV 1080, which are not cross-compatible.
HDV can be played back in HDV VTRs. These are often able to support other formats such as DV and DVCAM.
Users:
Amateur/Professional
File Systems:
Common Manufacturers:
Format developed by JVC, Sony, Canon and Sharp.
Unlike the other DV enhancements, HDV uses MPEG-2 compression rather than DV encoding. Any DV cassette can contain HDV format video, but some are sold with HDV branding on them.
There are two different types of HDV: HDV 720p (HD1, made by JVC) and HDV 1080 (HD2, made by Sony and Canon). HDV 1080 devices are not generally compatible with HDV 720p devices. The type of HDV used is not always identified on the cassette itself, as it depends on the camcorder used rather than the cassette.
Recognition
HDV is a tape only format which can be recorded on normal DV cassettes. Some MiniDV cassettes with lower dropout rates are indicated as being for HDV, either with text or the HDV logo. These are not essential for recording HDV video.

 

-Rebecca Nielsen

Media Recognition: DV part 2

DV (encoding)

Type:
Digital videotape cassette encoding
Introduced:
1995
Active:
Yes, but tapeless formats such as MPEG-1, MPEG-2 and MPEG-4 are becoming more popular.
Cessation:
Capacity:
MiniDV cassettes can hold up to 80/120 minutes SP/LP. Medium cassette size can hold up to 3.0/4.6 hrs SP/LP. Files sizes can be up to 1GB per 4 minutes of recording.
Compatibility:
DV format is widely adopted.
Cassettes recorded in the DV format can be played back on DVCAM, DVCPRO and HDV replay devices. However, LP recordings cannot be played back in these machines.
Users:
DV is aimed at a consumer market – may also be used by ‘prosumer’ film makers.
File Systems:
Common Manufacturers:
A consortium of over 60 manufacturers including Sony, Panasonic, JVC, Canon, and Sharp.
DV has a track width of 10 microns and a tape speed of 18.81mm/sec. It can be found on any type of DV cassette, regardless of branding, although most commonly it is the format used on MiniDV cassettes.
Recognition
DV cassettes are usually found in the small size, known as MiniDV. Medium size (97.5 × 64.5 × 14.6 mm) DV cassettes are also available, although these are not as popular as MiniDV. DV cassettes are labelled with the DV logo.
DVCPRO (encoding)
Type:
Digital videotape cassette encoding
Introduced:
1995 (DVCPRO), 1997 (DVCPRO 50), 2000 (DVCPRO HD)
Active:
Yes, but few new camcorders are being produced.
Cessation:
Capacity:
126 minutes (large), 66 minutes (medium).
Compatibility:
DVCPRO is an enhancement of the widely adopted DV format, and uses the same encoding.
Cassettes recorded in DVCPRO format can be played back only in DVCPRO Video Tape Recorders (VTRs) and some DVCAM VTRs.
Users:
Professional / Industrial; designed for electronic news gathering
File Systems:
Common Manufacturers:
Panasonic, also Philips, Ikegami and Hitachi.
DVCPRO is Panasonic’s enhancement of the DV format, which is aimed at a professional market. DVCPRO uses the same encoding as DV, but it features ‘locked’ audio, and uses 4:1:1 sampling instead of 4:2:0. It has an 18 micron track width, and a tape speed of 33.82 mm/sec which makes it more robust. DVCPRO uses Metal Particle (MP) tape rather than Metal Evaporate( ME) to improve durability.

DVCPRO 50 and DVCPRO HD are further developments of DVCPRO, which use the equivalent of 2 or 4 DV codecs in parallel to increase the video data rate.

Any DV cassette can contain DVCPRO format video, but some are sold with DVCPRO branding on them.

Recognition
DVCPRO branded cassettes come in medium (97.5 × 64.5 × 14.6mm) or large (125 × 78 × 14.6mm) cassette sizes. The medium size is for use in camcorders, and the large size in editing and recording decks. DVCPRO 50 and DVCPRO HD branded cassettes are extra-large cassettes (172 x 102 x 14.6mm). Tape width is ¼”.

DVCPRO labelled cassettes have different coloured tape doors depending on their type; DVCPRO has a yellow tape door, DVCPRO50 has a blue tape door, and DVCPRO HD has a red tape door.

Images of DVCPRO cassettes are available at the Panasonic website.

-Rebecca Nielsen

Media Recognition: DV part 1

DV can be used to refer to both a digital tape format, and a codec for digital video. DV tape usually carries video encoded with the DV codec, although it can hold any type of data. The DV format was developed in the mid 1990s by a consortium of video manufacturers, including Sony, JVC and Panasonic, and quickly became the de facto standard for home video production after introduction in 1995. Videos are recorded in .dv or .dif formats, or wrapped in an AVI, QuickTime or MXF container. These can be easily transferred to a computer with no loss of data over an IEEE 1394 (Fire Wire) connection.

DV tape is ¼ inch (6.35mm) wide. DV cassettes come in four different sizes: Small, also known as MiniDV (66 x 48 x 12.2 mm), medium (97.5 × 64.5 × 14.6 mm), large (125.1 x 78 x 14.6 mm), and extra-large (172 x 102 x 14.6 mm). MiniDV is the most popular cassette size.

DV cassettes can be encoded with one of four formats; DV, DVCAM, DVCPRO, or HDV. DV is the original encoding, and is used in consumer devices. DVCPRO and DVCAM were developed by Panasonic and Sony respectively as an enhancement of DV, and are aimed at a professional market. The basic encoding algorithm is the same as with DV, but a higher track width (18 and 15 microns versus DV’s 10 micron track width) and faster tape speed means that these formats are more robust and better suited to professional users. HDV is a high-definition variant, aimed at professionals and consumers, which uses MPEG-2 compression rather than the DV format.

Depending on the recording device, any of the four DV encodings can be recorded on any size DV cassette. However, due to different recording speeds, the formats are not always backwards compatible. A cassette recorded in an enhanced format, such as HDV, DVCAM or DVCPRO, will not play back on a standard DV player. Also, as they are supported by different companies, there are some issues with playing back a DVCPRO cassette on DVCAM equipment, and vice versa.

Although all DV cassette sizes can record any format of DV, some are marketed specifically as being of a certain type; e.g. DVCAM. The guide below looks at some of the most common varieties of DV cassette that might be encountered, and the encodings that may be used with them. It is important to remember that any type of encoding may be found on any kind of cassette, depending on what system the video was recorded on.

MiniDV (cassette)

Type:
Digital videotape cassette
Introduced:
1995
Active:
Yes, but is being replaced in popularity by hard disk and flash memory recording. At the International Consumer Electronics Show 2011 no camcorders were presented which record on tape.
Cessation:
Capacity:
Up to 80 minutes SP / 120 minutes LP, depending on the tape used; 60/90 minutes SP/LP is standard. This can also depend on the encoding used (see further entries). Files sizes can be up to 1GB per 4 minutes of recording.
Compatibility:
DV file format is widely adopted. Requires Fire Wire (IEEE 1394) port for best transfer.
Users:
Consumer and ‘Prosumer’ film makers, some professionals.
File Systems:
Common Manufacturers:
A consortium of over 60 manufacturers including Sony, Panasonic, JVC, Canon, and Sharp

MiniDV refers to the size of the cassette; as noted above, it can come with any encoding. As a consumer format they generally use DV encoding. DVCAM and HDV cassettes also come in MiniDV size.

MiniDV is the most popular DV cassette, and is used for consumer and semi-professional (‘prosumer’) recordings due to its high quality.

Recognition

These cassettes are the small cassette size, measuring 66 x 48 x 12.2mm. Tape width is ¼”. They carry the MiniDV logo, as seen below:

-Rebecca Nielsen

Preserving Digital Sound and Vision: A Briefing 8th April 2011

Last Friday I went along to the DPC briefing Preserving Digital Sound and Vision. I was particularly interested in the event because of digital video files currently held on DVD media at the Bodleian.

After arriving at the British Library and collecting my very funky Save the Bits DPC badge I sat down to listen to a packed programme of speakers. The morning talks gave an overview of issues associated with preserving audio-visual resources. We began with Nicky Whitsed from the Open University who spoke about the nature of the problem of preserving audio-visual content; a particularly pertinent issue for the OU who have 40 years of audio-visual teaching resources to deal with. Richard Ranft then gave a fascinating insight into the history and management of the British Library Sound Archive. He played a speech from Nelson Mandela’s 1964 trial to emphasise the value of audio preservation. Next Stephen Gray from JISC Digital Media spoke about how students are using audio-visual content in their research. He mentioned the difficulties researchers find when citing videos, especially those on YouTube that may disappear at any time! To round off the morning John Zubrycki from BBC R and D spoke about Challenges and Solutions in Broadcast Archives. One of the many interesting facts that he mentioned was that subtitle files originally produced by the BBC for broadcast have been used as a tool for search and retrieval of video content.

After enjoying lunch and the beautiful sunny weather on the British Library terrace we moved onto the afternoon programme based on specific projects and tools. Richard Wright of the BBC spoke about the Presto Centre and the tools it has developed to help with audio-visual preservation. He also spoke about the useful digital preservation tools available online via Presto Space. Sue Allcock and James Alexander then discussed the Outcomes and Lessons learnt from the Access to Video Assets Project at the Open University which makes past video content from the Open University’s courses available to OU staff through a Fedora repository. Like the BBC, discovering subtitle files has allowed the OU to index their audio-visual collections. Finally Simon Dixon from the Centre for Digital Music Queen Mary University spoke about emerging tools for digital sound.

A final wide ranging discussion about collaboration and next steps followed which included discussion about storage as well as ideas for a future event addressing the contexts of audio-visual resources. I left the event with my mind full of new information and lots of pointers for places to look to help me consider the next steps for our digital video collections… watch this space.

-Emma Hancox

Media players and the reader interface…

This is quite a long post, so I’m going to put the final line at the top too in case you don’t read that far… 😉

Your thoughts on media players would be most welcome!

The trouble, um, I mean, beauty of digital collections is that they redefine what a “manuscript” is. This is nothing new. Once upon a time someone somewhere probably upset the apple cart when they arrived at the hallowed doors with a basket full of photographs. Now we have video, audio and images, all of which can be encoded in any number of “standard” ways. (Not to mention a zillion different binary formats for just about any purpose you can imagine from sheet music to the latest car designs, which may well require more than just document-like presentation too – 3D models for example). These new manuscripts bring challenges for preservation, of course, but they also present challenges for presentation.

To address this, I’ve been learning more about media players in browsers with a view to picking one for the reader interface. I’m no expert in this field, so here is my layman’s consideration of what I’ve found out and if you want to read more then this is great!

The traditional method to render audio/video in browsers, which pre-dates their ability to handle video themselves, is to use a browser plug-in, either directly (for example VLC plugin) or (more commonly) to build on top of Flash (eg. Flowplayer) or Java (eg. Cortado). The exact mark-up required to use these players varies. Some will simply use the “embed” tag and others have JavaScript libraries to simplify their usage and allow for graceful degradation in the event that the browser does not have the correct plug-in and/or understand/run JavaScript. (This may be an issue when we deploy the interface into a reading room with machines we do not control the configuration of).

But the times, they are a-changin’. Just as old browsers knew what to do when presented with an “img” tag, most modern browsers are beginning to support HTML5’s “video” and “audio” tags, allowing the browser itself to handle the playback rather than farming this out to a plug-in. (For more on HTML5 generally see this presentation – the video tag is mentioned at about 58 minutes in). As an added bonus of bringing video into the browser in this way is it has inspired folks to build media players that manipulate the Web page to add the correct mark-up, be it a video tag, an embed, or whatever to play the media. This is currently being used to generate some nice media players that’ll use the browser, the Flash-plugin, or whatever is available (see OpenVideoPlayer and OSMPlayer).

So now we get to the crux of it. What should we do for the reader interface? Go old-school (and annoy Steve Jobs) and use a Flash-based player? Adopt the new ways of HTML5? Insist on an Open Source player? Buy something in?

To work out the answer I did a bit of investigating and have installed most of the players mentioned thus far in this post – Flowplayer, OSMPlayer, video-tag only, VLC and Cortado, as well as JWPlayer.

Flowplayer uses the Flash-plugin to play Flash video (and, with an additional plug-in, MP3 audio) – it does not support Ogg. It is very simple to use and very slick to look at. It is open source, released under GPL3 with an additional (and reasonable) “attribution clause” which basically means the Flowplayer logo must appear on the player unless you pay extra.

JWPlayer works much like Flowplayer (though there is also a beta HTML5 video player in the making) and seems pretty good. While the source code is available, it is not clear if this is an open source product or otherwise – the source files do not include a LICENSE.txt or any boilerplate. Probably I’m just missing something there though, and JWPlayer seems a good choice if you don’t mind Flash.

OSMPlayer is also open source and has numerous options for installation including a Drupal module (untested), a PHP library and a “stand-alone” configuration. In theory it supports lots of different audio and video formats and uses several divs to create a nice browser based player. Unfortunately, following the guidelines for both PHP and stand-alone configurations, I could not get it to work on my test server.

Video-tag only works pretty well with Firefox 3.6 on Ubuntu 10.04 and is very easy to include in a Web-page. Unfortunately it isn’t nearly as slick at playback as Flowplayer – there is a delay in starting the video and it is unclear what is going on.

The VLC plug-in is also open source and seems to work pretty well and should be able to handle many different formats, but it isn’t nearly as refined as other players and the provided example code fails to stop the video or make it full-screen. The VLC desktop player is wonderful, but I’m not convinced by the Firefox plug-in.

Cortado is a Java-applet provided to play Ogg Theora among other things. Usage is very simple – you just add an applet tag to the page – but playback is jerky, slow and lacked sound. I do not know if my machine is to blame for this or if it is the player itself so will have to investigate further.

Were I sat on and forced to make a choice I think I’d struggle. Flowplayer is slick to use and easy to implement, but requires we convert everything to Flash video or MP3 (mind you, most media will arrive in suitable formats I imagine). JWPlayer is very similar in this regard. I’d like to adopt the video-tag as this supports a wide range of formats, including open ones, but currently the experience is not very smooth and refinements in this area provided by things like OSMPlayer are still in their early stages of development. JWPlayer’s HTML5 offering is still beta for example.

I guess my feeling for now is to either go with Flowplayer (and swallow the conversions required – actually pretty easy with ffmpeg) or spend a bit of time with OpenVideoPlayer’s HTML5 work and the video tag. At this stage I think we probably need both working in the interface and see where the better user experience is…

I should throw one more thing into the pot – the problem of formats. Video and audio files are complicated beasts consisting of containers and tracks and such – a bit like cassettes! The contents of these containers are encoded in a variety of ways, each requiring different software to decode and render their content. We have the same problem with documents and we solve that by converting all the text-based materials we get into PDFs (for presentation before anyone starts worrying about the preservation implications of PDF!) and use a PDF plug-in to display them.

Can we do the same with our audio/video material and if we can, what format (I’m using “format” as a general term to mean “container/encoding”!) do we use? (Victoria has already done some work along these lines, creating WAVs for storage and MP3s for presentation, from audio CDs). Is there any additional concerns given that most born-digital video/audio is likely to arrive at our doors in a compressed format? Should we uncompress it? Is such a thing even possible? Should we (and do we have the processing power to) convert all audio/video materials to open formats for both preservation and presentation purposes?

We’re going to raise this final question at our next Library developer meeting and see what folks think. In theory we can delay the decision because most browsers and their plug-ins handle multiple formats, but perhaps we should have a standard delivery format much like we currently have PDF?

Oh dear. I started writing this post with the hope of finding all the answers! I have found out a lot about media players at least, which can only be a good thing, and I’ve also found out that that state of the art is not quite as far along as the proponents of HTML5 killing Flash would like us to believe – though there is good work going on here and this is the future. I’m also unclear just how much my experience of these things is hindered by using Ubuntu – I often wrestle with the playback of media files under Linux! 🙂

Still, I think we’re further along, nearer an answer and at least in a place to know where to start testing…

Your thoughts on media players would be most welcome! 🙂

-Peter Cliff

Academic Earth

Academic Earth presents ‘thousands of video lectures from the world’s top scholars’. So far, contributors are from top U.S. universities: Berkeley, Harvard, MIT, Princeton, Stanford and Yale. There is scope for expansion and the Academic Earth team are inviting new partners to contribute.

This is a great idea, but my main reason for linking to Academic Earth is that I rather like the interface. It feels very clean and it’s easy to navigate.

-Susan Thomas