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46 <h3>Ben Hutchings</h3>
51 <h1>What is DVswitch?</h1>
52 <ul class="incremental">
54 A software system that supports video mixing, recording and streaming
57 Designed particularly for the needs of technical conferences that
58 want to record and stream on a limited budget. Now used more
59 widely, often without streaming.
62 Mixing is <em>live</em> - a requirement for streaming, and a way to
63 avoid the need for extensive editing after the event
66 Mixing is <em>interactive</em> - a requirement for good coverage of
67 presenters, audience and slides, but very limited in other
74 <h1>What is DVswitch <em>not</em>?</h1>
76 There are limited developer resources and limited goals for
77 DVswitch. It is never intended to be:
79 <ul class="incremental">
81 A general video editor
84 An audio mixer (but it does implement audio dubbing and level monitoring)
87 A complete recording and publishing system
90 <p class="incremental">
91 These are all better handled by other software and
97 <h1>The 'DV' in DVswitch</h1>
99 The name refers to the DV formats used by many video cameras:
103 <th>Profile</th><th>Specification</th><th>Video codec</th><th>Supported</th>
106 <td>Basic DV</td><td>IEC 61834</td><td>DV 25</td><td>yes</td>
109 <td>DVCAM</td><td>Sony proprietary</td><td>DV 25</td><td>probably</td>
112 <td>DVCPRO</td><td>SMPTE 314M</td><td>DV 25</td><td>probably</td>
115 <td>DVCPRO50</td><td>SMPTE 314M</td><td>DV 50</td><td>not yet</td>
118 <td>DVCPRO HD</td><td>SMPTE 370M</td><td>DV 100</td><td>not yet</td>
121 <td>HDV</td><td>IEC 61834</td><td>MPEG-2</td><td>no</td>
125 DV video codecs compress each frame separately (unlike MPEG)
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129 The lack of interframe compression means there is relatively
130 little delay between camera and mixer and we can cut between
131 sources without having to decode all sources all the time.
132 In fact, DVswitch doesn't need to decode even a single source at
133 full frame rate if you just cut between sources without using
137 Unfortunately, most of today's consumer cameras don't have DV
138 output and may not provide live video output at all.
144 <h1>Overview of the system</h1>
146 A simplified view of the typical components:
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153 <ul class="incremental">
155 Source types: firewire/USB DV device, ALSA capture device,
159 Physical sources are spread around room and connected to the
160 mixer via TCP/IP networking
163 Original protocol: mixer runs a network server; sources run as
164 clients and send DIF over TCP
165 <ul class="incremental">
167 Requires a script to coordinate mixer and source startup -
168 an annoying complication
171 Improvement: tally lights
175 Next release: sources run as RTP/RTSP servers and mixer
176 connects to them as a client
177 <ul class="incremental">
179 No custom scripts required; just configuration files
188 <ul class="incremental">
190 Sink types: DIF files, pipe to arbitrary command
193 Also connected using TCP/IP networking, though this is not such
194 a good idea for recording
197 Original protocol: mixer runs a network server; sinks run
198 as clients and receive DIF over TCP
199 <ul class="incremental">
201 Improvement: sink reports whether it will record; mixer can
202 start, stop and cut recording
207 Next release: file and pipe sinks built into mixer along with an
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