章 7. 多媒體

7.1. 概述

FreeBSD 廣泛地支援各種音效卡, 讓使用者可以享受來自電腦上的高傳真音質(Hi-Fi), 此外還包括了錄製和播放 MPEG Audio Layer 3 (MP3)、 Waveform Audio File (WAV)、Ogg Vorbis 以及其他許多種格式聲音的能力。同時 FreeBSD Port 套件集也包含了許多可讓您可以錄音、編修音效以及控制 MIDI 配備的應用程式。

FreeBSD 也能播放一般的視訊檔和 DVD。 FreeBSD Port 套件集中含有可編碼、轉換以及播放格種影像媒體的應用程式。

本章會說明如何設定 FreeBSD 上的音效卡、影像播放器、電視卡及掃描器。同時會說明有那些應用程式可以使用這些裝置。

讀完這章,您將了解:

  • 設定 FreeBSD 上的音效卡。

  • 音效設定疑難排解。

  • 播放、錄製 MP3 及其他聲音檔案格式。

  • FreeBSD 系統播放影像的準備工具。

  • 播放 DVD 的 .mpg.avi 檔。

  • 擷取(Rip) CD 和 DVD的內容至檔案。

  • 設定電視卡。

  • 在 FreeBSD 安裝 MythTV

  • 設定影像掃描機。

  • 設定藍芽耳機。

在開始閱讀這章之前,您需要:

7.2. 設定音效卡

開始設定之前,必須先知道你的音效卡型號、晶片為何。 FreeBSD 支援許多種音效卡,請檢查支援的音效硬體表 Hardware Notes,以確認你的音效卡是否支援以及如何在 FreeBSD 上驅動。

要使用音效裝置,必須要載入正確的驅動程式才行。最簡單方式就是以 kldload(8) 來載入核心模組。以下範例示範載入 Intel 規格內建的音效晶片驅動程式:

# kldload snd_hda

要開機時自動載入驅動程式,需將驅動程式加到 /boot/loader.conf 檔,以此驅動程式為例:

snd_hda_load="YES"

其他可用的音效卡模組清單列於 /boot/defaults/loader.conf。當不確認要使用何種驅動程式時,可載入 snd_driver 模組:

# kldload snd_driver

它是 metadriver 會載入所有最通用的音效驅動程式並且用來加速尋找正確的驅動程式。也可以把 metadriver 加入 /boot/loader.conf 檔來載入所有音效驅動程式。

要知道載入 snd_driver metadriver 後使用了那個音效卡驅動程式,請輸入 cat /dev/sndstat

7.2.1. 設定自訂核心支援音效

This section is for users who prefer to statically compile in support for the sound card in a custom kernel. For more information about recompiling a kernel, refer to 設定 FreeBSD 核心.

When using a custom kernel to provide sound support, make sure that the audio framework driver exists in the custom kernel configuration file:

device sound

Next, add support for the sound card. To continue the example of the built-in audio chipset based on the Intel specification from the previous section, use the following line in the custom kernel configuration file:

device snd_hda

Be sure to read the manual page of the driver for the device name to use for the driver.

Non-PnP ISA sound cards may require the IRQ and I/O port settings of the card to be added to /boot/device.hints. During the boot process, loader(8) reads this file and passes the settings to the kernel. For example, an old Creative SoundBlaster™ 16 ISA non-PnP card will use the snd_sbc(4) driver in conjunction with snd_sb16. For this card, the following lines must be added to the kernel configuration file:

device snd_sbc
device snd_sb16

If the card uses the 0x220 I/O port and IRQ 5, these lines must also be added to /boot/device.hints:

hint.sbc.0.at="isa"
hint.sbc.0.port="0x220"
hint.sbc.0.irq="5"
hint.sbc.0.drq="1"
hint.sbc.0.flags="0x15"

The syntax used in /boot/device.hints is described in sound(4) and the manual page for the driver of the sound card.

The settings shown above are the defaults. In some cases, the IRQ or other settings may need to be changed to match the card. Refer to snd_sbc(4) for more information about this card.

7.2.2. 測試音效

After loading the required module or rebooting into the custom kernel, the sound card should be detected. To confirm, run dmesg | grep pcm. This example is from a system with a built-in Conexant CX20590 chipset:

pcm0: <NVIDIA (0x001c) (HDMI/DP 8ch)> at nid 5 on hdaa0
pcm1: <NVIDIA (0x001c) (HDMI/DP 8ch)> at nid 6 on hdaa0
pcm2: <Conexant CX20590 (Analog 2.0+HP/2.0)> at nid 31,25 and 35,27 on hdaa1

The status of the sound card may also be checked using this command:

# cat /dev/sndstat
FreeBSD Audio Driver (newpcm: 64bit 2009061500/amd64)
Installed devices:
pcm0: <NVIDIA (0x001c) (HDMI/DP 8ch)> (play)
pcm1: <NVIDIA (0x001c) (HDMI/DP 8ch)> (play)
pcm2: <Conexant CX20590 (Analog 2.0+HP/2.0)> (play/rec) default

The output will vary depending upon the sound card. If no pcm devices are listed, double-check that the correct device driver was loaded or compiled into the kernel. The next section lists some common problems and their solutions.

If all goes well, the sound card should now work in FreeBSD. If the CD or DVD drive is properly connected to the sound card, one can insert an audio CD in the drive and play it with cdcontrol(1):

% cdcontrol -f /dev/acd0 play 1

Audio CDs have specialized encodings which means that they should not be mounted using mount(8).

Various applications, such as audio/workman, provide a friendlier interface. The audio/mpg123 port can be installed to listen to MP3 audio files.

Another quick way to test the card is to send data to /dev/dsp:

% cat filename > /dev/dsp

where filename can be any type of file. This command should produce some noise, confirming that the sound card is working.

The /dev/dsp* device nodes will be created automatically as needed. When not in use, they do not exist and will not appear in the output of ls(1).

7.2.3. 設定藍芽音效裝置

Connecting to a Bluetooth device is out of scope for this chapter. Refer to 藍牙 for more information.

To get Bluetooth sound sink working with FreeBSD’s sound system, users have to install audio/virtual_oss first:

# pkg install virtual_oss

audio/virtual_oss requires cuse to be loaded into the kernel:

# kldload cuse

To load cuse during system startup, run this command:

# sysrc -f /boot/loader.conf cuse_load=yes

To use headphones as a sound sink with audio/virtual_oss, users need to create a virtual device after connecting to a Bluetooth audio device:

# virtual_oss -C 2 -c 2 -r 48000 -b 16 -s 768 -R /dev/null -P /dev/bluetooth/headphones -d dsp

headphones in this example is a hostname from /etc/bluetooth/hosts. BT_ADDR could be used instead.

請參考 virtual_oss(8) 取得更多資訊。

7.2.4. 疑難排解音效

常見錯誤訊息 lists some common error messages and their solutions:

表 1. 常見錯誤訊息
錯誤解決方式

sb_dspwr(XX) timed out

The I/O port is not set correctly.

bad irq XX

The IRQ is set incorrectly. Make sure that the set IRQ and the sound IRQ are the same.

xxx: gus pcm not attached, out of memory

There is not enough available memory to use the device.

xxx: can’t open /dev/dsp!

Type fstat | grep dsp to check if another application is holding the device open. Noteworthy troublemakers are esound and KDE’s sound support.

Modern graphics cards often come with their own sound driver for use with HDMI. This sound device is sometimes enumerated before the sound card meaning that the sound card will not be used as the default playback device. To check if this is the case, run dmesg and look for pcm. The output looks something like this:

...
hdac0: HDA Driver Revision: 20100226_0142
hdac1: HDA Driver Revision: 20100226_0142
hdac0: HDA Codec #0: NVidia (Unknown)
hdac0: HDA Codec #1: NVidia (Unknown)
hdac0: HDA Codec #2: NVidia (Unknown)
hdac0: HDA Codec #3: NVidia (Unknown)
pcm0: <HDA NVidia (Unknown) PCM #0 DisplayPort> at cad 0 nid 1 on hdac0
pcm1: <HDA NVidia (Unknown) PCM #0 DisplayPort> at cad 1 nid 1 on hdac0
pcm2: <HDA NVidia (Unknown) PCM #0 DisplayPort> at cad 2 nid 1 on hdac0
pcm3: <HDA NVidia (Unknown) PCM #0 DisplayPort> at cad 3 nid 1 on hdac0
hdac1: HDA Codec #2: Realtek ALC889
pcm4: <HDA Realtek ALC889 PCM #0 Analog> at cad 2 nid 1 on hdac1
pcm5: <HDA Realtek ALC889 PCM #1 Analog> at cad 2 nid 1 on hdac1
pcm6: <HDA Realtek ALC889 PCM #2 Digital> at cad 2 nid 1 on hdac1
pcm7: <HDA Realtek ALC889 PCM #3 Digital> at cad 2 nid 1 on hdac1
...

In this example, the graphics card (NVidia) has been enumerated before the sound card (Realtek ALC889). To use the sound card as the default playback device, change hw.snd.default_unit to the unit that should be used for playback:

# sysctl hw.snd.default_unit=n

where n is the number of the sound device to use. In this example, it should be 4. Make this change permanent by adding the following line to /etc/sysctl.conf:

hw.snd.default_unit=4

7.2.5. 使用多個音效來源

It is often desirable to have multiple sources of sound that are able to play simultaneously. FreeBSD uses "Virtual Sound Channels" to multiplex the sound card’s playback by mixing sound in the kernel.

Three sysctl(8) knobs are available for configuring virtual channels:

# sysctl dev.pcm.0.play.vchans=4
# sysctl dev.pcm.0.rec.vchans=4
# sysctl hw.snd.maxautovchans=4

This example allocates four virtual channels, which is a practical number for everyday use. Both dev.pcm.0.play.vchans=4 and dev.pcm.0.rec.vchans=4 are configurable after a device has been attached and represent the number of virtual channels pcm0 has for playback and recording. Since the pcm module can be loaded independently of the hardware drivers, hw.snd.maxautovchans indicates how many virtual channels will be given to an audio device when it is attached. Refer to pcm(4) for more information.

The number of virtual channels for a device cannot be changed while it is in use. First, close any programs using the device, such as music players or sound daemons.

The correct pcm device will automatically be allocated transparently to a program that requests /dev/dsp0.

7.2.6. 設定混音器頻道的預設值

The default values for the different mixer channels are hardcoded in the source code of the pcm(4) driver. While sound card mixer levels can be changed using mixer(8) or third-party applications and daemons, this is not a permanent solution. To instead set default mixer values at the driver level, define the appropriate values in /boot/device.hints, as seen in this example:

hint.pcm.0.vol="50"

This will set the volume channel to a default value of 50 when the pcm(4) module is loaded.

7.3. MP3 音樂

This section describes some MP3 players available for FreeBSD, how to rip audio CD tracks, and how to encode and decode MP3s.

7.3.1. MP3 播放器

A popular graphical MP3 player is Audacious. It supports Winamp skins and additional plugins. The interface is intuitive, with a playlist, graphic equalizer, and more. Those familiar with Winamp will find Audacious simple to use. On FreeBSD, Audacious can be installed from the multimedia/audacious port or package. Audacious is a descendant of XMMS.

The audio/mpg123 package or port provides an alternative, command-line MP3 player. Once installed, specify the MP3 file to play on the command line. If the system has multiple audio devices, the sound device can also be specified:

# mpg123 -a /dev/dsp1.0 Foobar-GreatestHits.mp3
High Performance MPEG 1.0/2.0/2.5 Audio Player for Layers 1, 2 and 3
        version 1.18.1; written and copyright by Michael Hipp and others
        free software (LGPL) without any warranty but with best wishes

Playing MPEG stream from Foobar-GreatestHits.mp3 ...
MPEG 1.0 layer III, 128 kbit/s, 44100 Hz joint-stereo

Additional MP3 players are available in the FreeBSD Ports Collection.

7.3.2. 擷取 CD 音軌

Before encoding a CD or CD track to MP3, the audio data on the CD must be ripped to the hard drive. This is done by copying the raw CD Digital Audio (CDDA) data to WAV files.

The cdda2wav tool, which is installed with the sysutils/cdrtools suite, can be used to rip audio information from CDs.

With the audio CD in the drive, the following command can be issued as root to rip an entire CD into individual, per track, WAV files:

# cdda2wav -D 0,1,0 -B

In this example, the -D 0,1,0 indicates the SCSI device 0,1,0 containing the CD to rip. Use cdrecord -scanbus to determine the correct device parameters for the system.

To rip individual tracks, use -t to specify the track:

# cdda2wav -D 0,1,0 -t 7

To rip a range of tracks, such as track one to seven, specify a range:

# cdda2wav -D 0,1,0 -t 1+7

To rip from an ATAPI (IDE) CDROM drive, specify the device name in place of the SCSI unit numbers. For example, to rip track 7 from an IDE drive:

# cdda2wav -D /dev/acd0 -t 7

Alternately, dd can be used to extract audio tracks on ATAPI drives, as described in 複製音樂 CD.

7.3.3. MP3 編碼與解碼

Lame is a popular MP3 encoder which can be installed from the audio/lame port. Due to patent issues, a package is not available.

The following command will convert the ripped WAV file audio01.wav to audio01.mp3:

# lame -h -b 128 --tt "Foo Song Title" --ta "FooBar Artist" --tl "FooBar Album" \
--ty "2014" --tc "Ripped and encoded by Foo" --tg "Genre" audio01.wav audio01.mp3

The specified 128 kbits is a standard MP3 bitrate while the 160 and 192 bitrates provide higher quality. The higher the bitrate, the larger the size of the resulting MP3. The -h turns on the "higher quality but a little slower" mode. The options beginning with --t indicate ID3 tags, which usually contain song information, to be embedded within the MP3 file. Additional encoding options can be found in the lame manual page.

In order to burn an audio CD from MP3s, they must first be converted to a non-compressed file format. XMMS can be used to convert to the WAV format, while mpg123 can be used to convert to the raw Pulse-Code Modulation (PCM) audio data format.

To convert audio01.mp3 using mpg123, specify the name of the PCM file:

# mpg123 -s audio01.mp3 > audio01.pcm

To use XMMS to convert a MP3 to WAV format, use these steps:

Procedure: Converting to WAV Format in XMMS . Launch XMMS. . Right-click the window to bring up the XMMS menu. . Select Preferences under Options. . Change the Output Plugin to "Disk Writer Plugin". . Press Configure. . Enter or browse to a directory to write the uncompressed files to. . Load the MP3 file into XMMS as usual, with volume at 100% and EQ settings turned off. . Press Play. The XMMS will appear as if it is playing the MP3, but no music will be heard. It is actually playing the MP3 to a file. . When finished, be sure to set the default Output Plugin back to what it was before in order to listen to MP3s again.

Both the WAV and PCM formats can be used with cdrecord. When using WAV files, there will be a small tick sound at the beginning of each track. This sound is the header of the WAV file. The audio/sox port or package can be used to remove the header:

% sox -t wav -r 44100 -s -w -c 2 track.wav track.raw

Refer to 建立與使用 CD 媒體 for more information on using a CD burner in FreeBSD.

7.4. 影片播放

Before configuring video playback, determine the model and chipset of the video card. While Xorg supports a wide variety of video cards, not all provide good playback performance. To obtain a list of extensions supported by the Xorg server using the card, run xdpyinfo while Xorg is running.

It is a good idea to have a short MPEG test file for evaluating various players and options. Since some DVD applications look for DVD media in /dev/dvd by default, or have this device name hardcoded in them, it might be useful to make a symbolic link to the proper device:

# ln -sf /dev/cd0 /dev/dvd

Due to the nature of devfs(5), manually created links will not persist after a system reboot. In order to recreate the symbolic link automatically when the system boots, add the following line to /etc/devfs.conf:

link cd0 dvd

DVD decryption invokes certain functions that require write permission to the DVD device.

To enhance the shared memory Xorg interface, it is recommended to increase the values of these sysctl(8) variables:

kern.ipc.shmmax=67108864
kern.ipc.shmall=32768

7.4.1. 偵測影像處理能力

There are several possible ways to display video under Xorg and what works is largely hardware dependent. Each method described below will have varying quality across different hardware.

Common video interfaces include:

  1. Xorg: normal output using shared memory.

  2. XVideo: an extension to the Xorg interface which allows video to be directly displayed in drawable objects through a special acceleration. This extension provides good quality playback even on low-end machines. The next section describes how to determine if this extension is running.

  3. SDL: the Simple Directmedia Layer is a porting layer for many operating systems, allowing cross-platform applications to be developed which make efficient use of sound and graphics. SDL provides a low-level abstraction to the hardware which can sometimes be more efficient than the Xorg interface. On FreeBSD, SDL can be installed using the devel/sdl20 package or port.

  4. DGA: the Direct Graphics Access is an Xorg extension which allows a program to bypass the Xorg server and directly alter the framebuffer. Because it relies on a low level memory mapping, programs using it must be run as root. The DGA extension can be tested and benchmarked using dga(1). When dga is running, it changes the colors of the display whenever a key is pressed. To quit, press q.

  5. SVGAlib: a low level console graphics layer.

7.4.1.1. XVideo

To check whether this extension is running, use xvinfo:

% xvinfo

XVideo is supported for the card if the result is similar to:

X-Video Extension version 2.2
  screen #0
  Adaptor #0: "Savage Streams Engine"
    number of ports: 1
    port base: 43
    operations supported: PutImage
    supported visuals:
      depth 16, visualID 0x22
      depth 16, visualID 0x23
    number of attributes: 5
      "XV_COLORKEY" (range 0 to 16777215)
              client settable attribute
              client gettable attribute (current value is 2110)
      "XV_BRIGHTNESS" (range -128 to 127)
              client settable attribute
              client gettable attribute (current value is 0)
      "XV_CONTRAST" (range 0 to 255)
              client settable attribute
              client gettable attribute (current value is 128)
      "XV_SATURATION" (range 0 to 255)
              client settable attribute
              client gettable attribute (current value is 128)
      "XV_HUE" (range -180 to 180)
              client settable attribute
              client gettable attribute (current value is 0)
    maximum XvImage size: 1024 x 1024
    Number of image formats: 7
      id: 0x32595559 (YUY2)
        guid: 59555932-0000-0010-8000-00aa00389b71
        bits per pixel: 16
        number of planes: 1
        type: YUV (packed)
      id: 0x32315659 (YV12)
        guid: 59563132-0000-0010-8000-00aa00389b71
        bits per pixel: 12
        number of planes: 3
        type: YUV (planar)
      id: 0x30323449 (I420)
        guid: 49343230-0000-0010-8000-00aa00389b71
        bits per pixel: 12
        number of planes: 3
        type: YUV (planar)
      id: 0x36315652 (RV16)
        guid: 52563135-0000-0000-0000-000000000000
        bits per pixel: 16
        number of planes: 1
        type: RGB (packed)
        depth: 0
        red, green, blue masks: 0x1f, 0x3e0, 0x7c00
      id: 0x35315652 (RV15)
        guid: 52563136-0000-0000-0000-000000000000
        bits per pixel: 16
        number of planes: 1
        type: RGB (packed)
        depth: 0
        red, green, blue masks: 0x1f, 0x7e0, 0xf800
      id: 0x31313259 (Y211)
        guid: 59323131-0000-0010-8000-00aa00389b71
        bits per pixel: 6
        number of planes: 3
        type: YUV (packed)
      id: 0x0
        guid: 00000000-0000-0000-0000-000000000000
        bits per pixel: 0
        number of planes: 0
        type: RGB (packed)
        depth: 1
        red, green, blue masks: 0x0, 0x0, 0x0

The formats listed, such as YUV2 and YUV12, are not present with every implementation of XVideo and their absence may hinder some players.

If the result instead looks like:

X-Video Extension version 2.2
screen #0
no adaptors present

XVideo is probably not supported for the card. This means that it will be more difficult for the display to meet the computational demands of rendering video, depending on the video card and processor.

7.4.2. 可處理影像的 Port 與套件

This section introduces some of the software available from the FreeBSD Ports Collection which can be used for video playback.

7.4.2.1. MPlayer 與 MEncoder

MPlayer is a command-line video player with an optional graphical interface which aims to provide speed and flexibility. Other graphical front-ends to MPlayer are available from the FreeBSD Ports Collection.

MPlayer can be installed using the multimedia/mplayer package or port. Several compile options are available and a variety of hardware checks occur during the build process. For these reasons, some users prefer to build the port rather than install the package.

When compiling the port, the menu options should be reviewed to determine the type of support to compile into the port. If an option is not selected, MPlayer will not be able to display that type of video format. Use the arrow keys and spacebar to select the required formats. When finished, press Enter to continue the port compile and installation.

By default, the package or port will build the mplayer command line utility and the gmplayer graphical utility. To encode videos, compile the multimedia/mencoder port. Due to licensing restrictions, a package is not available for MEncoder.

The first time MPlayer is run, it will create ~/.mplayer in the user’s home directory. This subdirectory contains default versions of the user-specific configuration files.

This section describes only a few common uses. Refer to mplayer(1) for a complete description of its numerous options.

To play the file testfile.avi, specify the video interfaces with -vo, as seen in the following examples:

% mplayer -vo xv testfile.avi
% mplayer -vo sdl testfile.avi
% mplayer -vo x11 testfile.avi
# mplayer -vo dga testfile.avi
# mplayer -vo 'sdl:dga' testfile.avi

It is worth trying all of these options, as their relative performance depends on many factors and will vary significantly with hardware.

To play a DVD, replace testfile.avi with dvd://N -dvd-device DEVICE, where N is the title number to play and DEVICE is the device node for the DVD. For example, to play title 3 from /dev/dvd:

# mplayer -vo xv dvd://3 -dvd-device /dev/dvd

The default DVD device can be defined during the build of the MPlayer port by including the WITH_DVD_DEVICE=/path/to/desired/device option. By default, the device is /dev/cd0. More details can be found in the port’s Makefile.options.

To stop, pause, advance, and so on, use a keybinding. To see the list of keybindings, run mplayer -h or read mplayer(1).

Additional playback options include -fs -zoom, which engages fullscreen mode, and -framedrop, which helps performance.

Each user can add commonly used options to their ~/.mplayer/config like so:

vo=xv
fs=yes
zoom=yes

mplayer can be used to rip a DVD title to a .vob. To dump the second title from a DVD:

# mplayer -dumpstream -dumpfile out.vob dvd://2 -dvd-device /dev/dvd

The output file, out.vob, will be in MPEG format.

Anyone wishing to obtain a high level of expertise with UNIX™ video should consult mplayerhq.hu/DOCS as it is technically informative. This documentation should be considered as required reading before submitting any bug reports.

Before using mencoder, it is a good idea to become familiar with the options described at mplayerhq.hu/DOCS/HTML/en/mencoder.html. There are innumerable ways to improve quality, lower bitrate, and change formats, and some of these options may make the difference between good or bad performance. Improper combinations of command line options can yield output files that are unplayable even by mplayer.

Here is an example of a simple copy:

% mencoder input.avi -oac copy -ovc copy -o output.avi

To rip to a file, use -dumpfile with mplayer.

To convert input.avi to the MPEG4 codec with MPEG3 audio encoding, first install the audio/lame port. Due to licensing restrictions, a package is not available. Once installed, type:

% mencoder input.avi -oac mp3lame -lameopts br=192 \
	 -ovc lavc -lavcopts vcodec=mpeg4:vhq -o output.avi

This will produce output playable by applications such as mplayer and xine.

input.avi can be replaced with dvd://1 -dvd-device /dev/dvd and run as root to re-encode a DVD title directly. Since it may take a few tries to get the desired result, it is recommended to instead dump the title to a file and to work on the file.

7.4.2.2. xine 影像播放器

xine is a video player with a reusable base library and a modular executable which can be extended with plugins. It can be installed using the multimedia/xine package or port.

In practice, xine requires either a fast CPU with a fast video card, or support for the XVideo extension. The xine video player performs best on XVideo interfaces.

By default, the xine player starts a graphical user interface. The menus can then be used to open a specific file.

Alternatively, xine may be invoked from the command line by specifying the name of the file to play:

% xine -g -p mymovie.avi

Refer to xine-project.org/faq for more information and troubleshooting tips.

7.4.2.3. Transcode 工具

Transcode provides a suite of tools for re-encoding video and audio files. Transcode can be used to merge video files or repair broken files using command line tools with stdin/stdout stream interfaces.

In FreeBSD, Transcode can be installed using the multimedia/transcode package or port. Many users prefer to compile the port as it provides a menu of compile options for specifying the support and codecs to compile in. If an option is not selected, Transcode will not be able to encode that format. Use the arrow keys and spacebar to select the required formats. When finished, press Enter to continue the port compile and installation.

This example demonstrates how to convert a DivX file into a PAL MPEG-1 file (PAL VCD):

% transcode -i input.avi -V --export_prof vcd-pal -o output_vcd
% mplex -f 1 -o output_vcd.mpg output_vcd.m1v output_vcd.mpa

The resulting MPEG file, output_vcd.mpg, is ready to be played with MPlayer. The file can be burned on a CD media to create a video CD using a utility such as multimedia/vcdimager or sysutils/cdrdao.

In addition to the manual page for transcode, refer to transcoding.org/cgi-bin/transcode for further information and examples.

7.5. 電視卡

電視卡 (TV card) 可以讓您用電腦來看無線、有線電視節目。許多卡都是透過 RCA 或 S-video 輸入端子來接收視訊,而且有些卡還可接收 FM 廣播的功能。

FreeBSD 可透過 bktr(4) 驅動程式,來支援 PCI 介面的電視卡,只要這些卡使用的是 Brooktree Bt848/849/878/879 或 Conexant CN-878/Fusion 878a 視訊擷取晶片。此外,要再確認哪些卡上所附的選台功能是否有支援,可以參考 bktr(4) 說明,以查看所支援的硬體清單。

7.5.1. 載入驅動程式

要用電視卡的話,就要載入 bktr(4) 驅動程式,這個可以透過在 /boot/loader.conf 檔加上下面這一行就可以了:

bktr_load="YES"

或者可以將電視卡支援靜態編譯到自訂的核心當中,若要這麼做則可在自訂核心設定檔加入以下行:

device	 bktr
device	iicbus
device	iicbb
device	smbus

之所以要加上這些額外的驅動程式,是因為卡的各組成部分都是透過 I2C 匯流排而相互連接的。接下來,請編譯、安裝新的核心 。

要測試調諧器 (Tuner) 是否被正確的偵測,請先重新啟動系統。電視卡應該會出現在開機訊息檔中,如同此範例:

bktr0: <BrookTree 848A> mem 0xd7000000-0xd7000fff irq 10 at device 10.0 on pci0
iicbb0: <I2C bit-banging driver> on bti2c0
iicbus0: <Philips I2C bus> on iicbb0 master-only
iicbus1: <Philips I2C bus> on iicbb0 master-only
smbus0: <System Management Bus> on bti2c0
bktr0: Pinnacle/Miro TV, Philips SECAM tuner.

該訊息會依硬體不同而有所不同。若必要,可以使用 sysctl(8) 系統偵測的參數或者自訂核心設定選項。例如要強制使用 Philips SECAM 調諧器則可加入下列行至自訂核心設定檔:

options OVERRIDE_TUNER=6

或使用 sysctl(8)

# sysctl hw.bt848.tuner=6

請參考 bktr(4) 查看 sysctl(8) 可用的參數說明及核心選項。

7.5.2. 好用的應用程式

To use the TV card, install one of the following applications:

  • multimedia/fxtv provides TV-in-a-window and image/audio/video capture capabilities.

  • multimedia/xawtv is another TV application with similar features.

  • audio/xmradio provides an application for using the FM radio tuner of a TV card.

More applications are available in the FreeBSD Ports Collection.

7.5.3. 疑難排解

If any problems are encountered with the TV card, check that the video capture chip and the tuner are supported by bktr(4) and that the right configuration options were used. For more support or to ask questions about supported TV cards, refer to the freebsd-multimedia mailing list.

7.6. MythTV

MythTV is a popular, open source Personal Video Recorder (PVR) application. This section demonstrates how to install and setup MythTV on FreeBSD. Refer to mythtv.org/wiki for more information on how to use MythTV.

MythTV requires a frontend and a backend. These components can either be installed on the same system or on different machines.

The frontend can be installed on FreeBSD using the multimedia/mythtv-frontend package or port. Xorg must also be installed and configured as described in X Window 系統. Ideally, this system has a video card that supports X-Video Motion Compensation (XvMC) and, optionally, a Linux Infrared Remote Control (LIRC)-compatible remote.

To install both the backend and the frontend on FreeBSD, use the multimedia/mythtv package or port. A MySQL™ database server is also required and should automatically be installed as a dependency. Optionally, this system should have a tuner card and sufficient storage to hold recorded data.

7.6.1. 硬體

MythTV uses Video for Linux (V4L) to access video input devices such as encoders and tuners. In FreeBSD, MythTV works best with USB DVB-S/C/T cards as they are well supported by the multimedia/webcamd package or port which provides a V4L userland application. Any Digital Video Broadcasting (DVB) card supported by webcamd should work with MythTV. A list of known working cards can be found at wiki.freebsd.org/WebcamCompat. Drivers are also available for Hauppauge cards in the multimedia/pvr250 and multimedia/pvrxxx ports, but they provide a non-standard driver interface that does not work with versions of MythTV greater than 0.23. Due to licensing restrictions, no packages are available and these two ports must be compiled.

The wiki.freebsd.org/HTPC page contains a list of all available DVB drivers.

7.6.2. 設定 MythTV 後端

要使用 Binary 套件安裝 MythTV 可:

# pkg install mythtv

或從 Port 套件集安裝:

# cd /usr/ports/multimedia/mythtv
# make install

Once installed, set up the MythTV database:

# mysql -uroot -p < /usr/local/shared/mythtv/database/mc.sql

Then, configure the backend:

# mythtv-setup

Finally, start the backend:

# sysrc mythbackend_enable=yes
# service mythbackend start

7.7. 影像掃描器

In FreeBSD, access to image scanners is provided by SANE (Scanner Access Now Easy), which is available in the FreeBSD Ports Collection. SANE will also use some FreeBSD device drivers to provide access to the scanner hardware.

FreeBSD supports both SCSI and USB scanners. Depending upon the scanner interface, different device drivers are required. Be sure the scanner is supported by SANE prior to performing any configuration. Refer to http://www.sane-project.org/sane-supported-devices.html for more information about supported scanners.

This chapter describes how to determine if the scanner has been detected by FreeBSD. It then provides an overview of how to configure and use SANE on a FreeBSD system.

7.7.1. 檢查掃描器

The GENERIC kernel includes the device drivers needed to support USB scanners. Users with a custom kernel should ensure that the following lines are present in the custom kernel configuration file:

device usb
device uhci
device ohci
device ehci

To determine if the USB scanner is detected, plug it in and use dmesg to determine whether the scanner appears in the system message buffer. If it does, it should display a message similar to this:

ugen0.2: <EPSON> at usbus0

In this example, an EPSON Perfection™ 1650 USB scanner was detected on /dev/ugen0.2.

If the scanner uses a SCSI interface, it is important to know which SCSI controller board it will use. Depending upon the SCSI chipset, a custom kernel configuration file may be needed. The GENERIC kernel supports the most common SCSI controllers. Refer to /usr/src/sys/conf/NOTES to determine the correct line to add to a custom kernel configuration file. In addition to the SCSI adapter driver, the following lines are needed in a custom kernel configuration file:

device scbus
device pass

Verify that the device is displayed in the system message buffer:

pass2 at aic0 bus 0 target 2 lun 0
pass2: <AGFA SNAPSCAN 600 1.10> Fixed Scanner SCSI-2 device
pass2: 3.300MB/s transfers

If the scanner was not powered-on at system boot, it is still possible to manually force detection by performing a SCSI bus scan with camcontrol:

# camcontrol rescan all
Re-scan of bus 0 was successful
Re-scan of bus 1 was successful
Re-scan of bus 2 was successful
Re-scan of bus 3 was successful

The scanner should now appear in the SCSI devices list:

# camcontrol devlist
<IBM DDRS-34560 S97B>              at scbus0 target 5 lun 0 (pass0,da0)
<IBM DDRS-34560 S97B>              at scbus0 target 6 lun 0 (pass1,da1)
<AGFA SNAPSCAN 600 1.10>           at scbus1 target 2 lun 0 (pass3)
<PHILIPS CDD3610 CD-R/RW 1.00>     at scbus2 target 0 lun 0 (pass2,cd0)

Refer to scsi(4) and camcontrol(8) for more details about SCSI devices on FreeBSD.

7.7.2. SANE 設定

The SANE system is split in two parts: the backends (graphics/sane-backends) and the frontends (graphics/sane-frontends or graphics/xsane). The backends provide access to the scanner. Refer to http://www.sane-project.org/sane-supported-devices.html to determine which backend supports the scanner. The frontends provide the graphical scanning interface. graphics/sane-frontends installs xscanimage while graphics/xsane installs xsane.

要由 Binary 套件安裝這兩個部份可:

# pkg install xsane sane-frontends

或由 Port 套件集安裝

# cd /usr/ports/graphics/sane-frontends
# make install clean
# cd /usr/ports/graphics/xsane
# make install clean

After installing the graphics/sane-backends port or package, use sane-find-scanner to check the scanner detection by the SANE system:

# sane-find-scanner -q
found SCSI scanner "AGFA SNAPSCAN 600 1.10" at /dev/pass3

The output should show the interface type of the scanner and the device node used to attach the scanner to the system. The vendor and the product model may or may not appear.

Some USB scanners require firmware to be loaded. Refer to sane-find-scanner(1) and sane(7) for details.

Next, check if the scanner will be identified by a scanning frontend. The SANE backends include scanimage which can be used to list the devices and perform an image acquisition. Use -L to list the scanner devices. The first example is for a SCSI scanner and the second is for a USB scanner:

# scanimage -L
device `snapscan:/dev/pass3' is a AGFA SNAPSCAN 600 flatbed scanner
# scanimage -L
device 'epson2:libusb:/dev/usb:/dev/ugen0.2' is a Epson GT-8200 flatbed scanner

In this second example, 'epson2:libusb:/dev/usb:/dev/ugen0.2' is the backend name (epson2) and /dev/ugen0.2 is the device node used by the scanner.

If scanimage is unable to identify the scanner, this message will appear:

# scanimage -L

No scanners were identified. If you were expecting something different,
check that the scanner is plugged in, turned on and detected by the
sane-find-scanner tool (if appropriate). Please read the documentation
which came with this software (README, FAQ, manpages).

If this happens, edit the backend configuration file in /usr/local/etc/sane.d/ and define the scanner device used. For example, if the undetected scanner model is an EPSON Perfection™ 1650 and it uses the epson2 backend, edit /usr/local/etc/sane.d/epson2.conf. When editing, add a line specifying the interface and the device node used. In this case, add the following line:

usb /dev/ugen0.2

Save the edits and verify that the scanner is identified with the right backend name and the device node:

# scanimage -L
device 'epson2:libusb:/dev/usb:/dev/ugen0.2' is a Epson GT-8200 flatbed scanner

Once scanimage -L sees the scanner, the configuration is complete and the scanner is now ready to use.

While scanimage can be used to perform an image acquisition from the command line, it is often preferable to use a graphical interface to perform image scanning. The graphics/sane-frontends package or port installs a simple but efficient graphical interface, xscanimage.

Alternately, xsane, which is installed with the graphics/xsane package or port, is another popular graphical scanning frontend. It offers advanced features such as various scanning modes, color correction, and batch scans. Both of these applications are usable as a GIMP plugin.

7.7.3. 掃描器權限

In order to have access to the scanner, a user needs read and write permissions to the device node used by the scanner. In the previous example, the USB scanner uses the device node /dev/ugen0.2 which is really a symlink to the real device node /dev/usb/0.2.0. The symlink and the device node are owned, respectively, by the wheel and operator groups. While adding the user to these groups will allow access to the scanner, it is considered insecure to add a user to wheel. A better solution is to create a group and make the scanner device accessible to members of this group.

This example creates a group called usb:

# pw groupadd usb

Then, make the /dev/ugen0.2 symlink and the /dev/usb/0.2.0 device node accessible to the usb group with write permissions of 0660 or 0664 by adding the following lines to /etc/devfs.rules:

[system=5]
add path ugen0.2 mode 0660 group usb
add path usb/0.2.0 mode 0666 group usb

Finally, add the users to usb in order to allow access to the scanner:

# pw groupmod usb -m joe

For more details refer to pw(8).


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