Posted by admin on January 21, 2015 under Tech Tips | 
Here’s a quick tip on using Mencoder profiles that serve as shortcuts for all of your favorite settings. This can save you a lot of time, especially when your encoding syntax is lengthy and difficult to remember.
Profiles are stored in the mencoder.conf file located in the appropriate place for your operating system. For Linux users, you can create a personalized file in your own home directory, ~/.mplayer/mencoder.conf.
Here’s the syntax you might use on a single-pass XviD project without using profiles.
mencoder -oac mp3lame -lameopts aq=0:q=0 -ovc xvid -xvidencopts
fixed_quant=2:max_key_interval=25:vhq=2:bvhq=1:chroma_opt:quant_type=mpeg
input.avi -o output.avi
Compare that with the following examples of some of my favorite profiles, and how easy it is to use them.
XviD Single-pass Profile Example
[xvid]
profile-desc="MPEG4/MP3 encoding"
ovc=xvid=1
xvidencopts=fixed_quant=2:max_key_interval=25:vhq=2:bvhq=1:chroma_opt=1:quant_type=mpeg
oac=mp3lame=1
lameopts=aq=0:q=0
mencoder -profile xvid input.avi -o output.avi
XviD 2-pass Profile Examples
[xvid-pass1]
profile-desc="MPEG4/MP3 encoding - PASS 1"
ovc=xvid=1
xvidencopts=pass=1:max_key_interval=25:turbo=1:vhq=0
nosound=1
o=/dev/null
passlogfile=xvid-pass1.log
[xvid-pass2]
profile-desc="MPEG4/MP3 encoding - PASS 2"
ovc=xvid=1
xvidencopts=pass=2:max_key_interval=25:vhq=2:bvhq=1:chroma_opt=1:quant_type=mpeg:bitrate=2000
oac=mp3lame=1
lameopts=aq=0:q=0
passlogfile=xvid-pass1.log
mencoder -profile xvid-pass1 input.avi
mencoder -profile xvid-pass2 input.avi -o output.avi
x264 2-pass Profile Examples
[x264-pass1]
profile-desc="x264 encoding - PASS 1"
ovc=x264=1
x264encopts=pass=1:threads=0:subq=1:frameref=1:bframes=3:b_pyramid=normal:weight_b=1:keyint=25
nosound=1
o=/dev/null
passlogfile=x264-pass1.log
[x264-pass2]
profile-desc="x264 encoding - PASS 2"
ovc=x264=1
x264encopts=pass=2:threads=0:subq=6:frameref=5:partitions=all:8x8dct=1:me=umh:bframes=3:b_pyramid=normal:weight_b=1:keyint=25:bitrate=2000
oac=mp3lame=1
lameopts=aq=0:q=0
passlogfile=x264-pass1.log
mencoder -profile x264-pass1 input.avi
mencoder -profile x264-pass2 input.avi -o output.avi
x264 Single-pass Profile Example
[x264]
profile-desc="x264 encoding"
ovc=x264=1
x264encopts=crf=20:threads=0:subq=6:frameref=5:partitions=all:8x8dct=1:me=umh:bframes=3:b_pyramid=normal:weight_b=1:keyint=25
aspect=16/9
oac=mp3lame=1
lameopts=aq=0:q=0
mencoder -profile x264 input.avi -o output.avi
Posted by admin on September 19, 2012 under Tech Tips |
If you would like to copy a DVD to an XviD video file using Linux, doing so from the command line offers a number of flexibility benefits over many graphical tools. Two fantastic tools for the job are lsdvd and mencoder. I like lsdvd because it provides a great deal of information in an easy to read format, and mencoder is just a phenomenal tool for multimedia encoding.
There are some pre-requisite applications you need in order to follow along. Be sure to install mplayer, mencoder, lsdvd, lame, and if your DVD’s are encrypted, the libdvdcss2 libraries. If using Ubuntu, Debian, etc, then all are available in the repositories, except libdvdcss2 which is available in the Medibuntu repositories.
Quick XviD Encoding Examples (For the Impatient)
In the following examples, we’ll use mencoder with the most basic of options, allowing mencoder to decide which video and audio streams to use. Mencoder’s choice may not be what you want, and the audio will also be converted to a high quality VBR stereo MP3. Adjust any settings as you see fit.
Single-Pass Encoding
Fixed Quantizer Value of 4 (Good quality, decent file size)
mencoder dvd:// -oac mp3lame -lameopts q=0:aq=0
-ovc xvid -xvidencopts fixed_quant=4:autoaspect -o video.avi
Fixed Quantizer Value of 2 (High quality, larger file size)
mencoder dvd:// -oac mp3lame -lameopts q=0:aq=0
-ovc xvid -xvidencopts fixed_quant=2:autoaspect -o video.avi
Two Pass Encoding
Pass 1: (no need for audio or quality settings such as bitrate)
mencoder dvd:// -nosound -passlogfile pass1.log
-ovc xvid -xvidencopts pass=1:turbo:autoaspect -o /dev/null
Pass 2 Option 1: (VBR ~ 1500 kbps)
mencoder dvd:// -oac mp3lame -lameopts q=0:aq=0 -passlogfile pass1.log
-ovc xvid -xvidencopts pass=2:autoaspect:bitrate=1500 -o video.avi
Pass 2 Option 2: (VBR ~ Restrict final video size to 1.5 Gb)
mencoder dvd:// -oac mp3lame -lameopts q=0:aq=0 -passlogfile pass1.log
-ovc xvid -xvidencopts pass=2:autoaspect:bitrate=-1500000 -o video.avi
Basic Source Selection Examples
If you are copying a DVD directly from a physical disc as the examples throughout this post will assume, the following two examples will work. The first automatically selects title 1, and the second specifies title 2.
mencoder dvd:// (other options)
mencoder dvd://2 (other options)
If you’re encoding a DVD from an ISO or similar image file, or have the contents of a DVD extracted to directory, use the -dvd-device option as shown below.
mencoder dvd:// -dvd-device video.iso (other options)
mencoder dvd:// -dvd-device /path/to/dvd_directory/ (other options)
Basic Audio Examples
To encode the selected audio stream to a high quality VBR stereo MP3 format.
mencoder dvd:// -oac mp3lame -lameopts q=0:aq=0 (other options)
If the source audio stream is encoded as AC3 or DTS 5.1 (6 Channels), you can simply copy the stream, but remember to specify 6 channels. The default is 2.
mencoder dvd:// -oac copy -channels 6 (other options)
To exclude all sound, which is useful for the first pass of a two-pass job, or if you prefer to multiplex the audio later, use the -nosound option.
mencoder dvd:// -nosound (other options)
Gathering Source Video Information for Informed Encoding Decisions
First you should identify which DVD title tracks are available, so you can determine which one you want to copy. Most DVDs will place the movie as the first track, but you may not always be that lucky. You can use lsdvd to list the number of titles, chapters, and audio tracks on your DVD.
lsdvd /dev/dvd
Disc Title: DVD_TITLE
Title: 01, Length: 01:26:08.200 Chapters: 13, Cells: 13, Audio streams: 02, Subpictures: 01
Title: 02, Length: 00:02:01.120 Chapters: 01, Cells: 01, Audio streams: 02, Subpictures: 01
Title: 03, Length: 00:02:26.120 Chapters: 01, Cells: 01, Audio streams: 02, Subpictures: 01
Longest track: 01
In the example above, we found that Title 01 is the longest at 1 hour 26 minutes, has 13 chapters and 2 audio streams.
Use lsdvd again to gather additional information about video properties of this specific title.
lsdvd -v -t 1 /dev/dvd
Disc Title: DVD_TITLE
Title: 01, Length: 01:26:08.200 Chapters: 13, Cells: 13, Audio streams: 02, Subpictures: 01
VTS: 01, TTN: 01, FPS: 25.00, Format: PAL, Aspect ratio: 4/3, Width: 720, Height: 576, DF: ?
From the output above, we see that this video is in the PAL format at 25.00 frames per second and an aspect ratio of 4/3. Use mplayer to play this title and verify it’s the one you want.
mplayer dvd://1
Gathering Source Audio Information
Use lsdvd to give you more detail on the available audio streams for the title you’re working on.
lsdvd -a -t 1 /dev/dvd
Disc Title: DVD_TITLE
Title: 01, Length: 01:26:08.200 Chapters: 13, Cells: 13, Audio streams: 02, Subpictures: 01
Audio: 1, Language: nl - Nederlands, Format: ac3, Frequency: 48000, Quantization: drc, Channels: 2, AP: 0, Content: Undefined, Stream id: 0x80
Audio: 2, Language: en - English, Format: ac3, Frequency: 48000, Quantization: drc, Channels: 2, AP: 0, Content: Undefined, Stream id: 0x81
The output above shows that there are two audio streams, both AC3 Dolby Digital, however only the second one is in English. Mencoder and mplayer allow you to specify your desired audio stream by language as shown in the following example.
mencoder dvd://1 -alang eng (other options)
If your source has multiple English streams, you can specify which particular audio ID (aid) you want. Mplayer can be used to display all available audio identifiers of a DVD. The following command is a little long but it should serve you well.
mplayer dvd://1 -identify -frames 0 -vo null 2>&1 | grep aid
audio stream: 0 format: ac3 (stereo) language: nl aid: 128.
audio stream: 1 format: ac3 (stereo) language: en aid: 129.
From the output above, the English AC3 audio stream we want is identified by aid 129. It can be specified when using mplayer and mencoder as shown below.
mencoder dvd://1 -aid 129 (other options)
Advanced Single-Pass XviD Encoding
As mentioned before, you can encode your video using a single-pass fixed quantizer mode. It may not be as efficient in size and quality as opposed to a two-pass method, but it can save some time and complexity. Here’s the more advanced encoding options I tend to use for virtually all of my XviD encoding jobs, coupled with the information we gathered from above. A fixed_quant value between 2 and 4 work very well. The lower the number the higher the quality and larger the resulting file size.
mencoder dvd://1 -alang eng -oac mp3lame -lameopts q=0:aq=0
-ovc xvid -xvidencopts fixed_quant=4:autoaspect:max_key_interval=25:
vhq=2:bvhq=1:trellis:hq_ac:chroma_me:chroma_opt:quant_type=mpeg
-o video.avi
I added a number of quality settings as discussed both in the mencoder man page and this useful link here.
One option that seems to lack a lot of documentation is the max_key_interval setting. It influences the seekability of the encoded video. By default, the max_key_interval is set to a value of 250, which adds an I-frame at a maximum interval of 250 frames. This equates to approximately every 10 seconds depending on the frame rate of your source video. I like to set the value to 25 which is pretty low and results in a slightly larger file, but provides a seek accuracy of about 1 second. That’s just my preference, so feel free to change it as you wish.
Advanced Two-Pass XviD Encoding
Using the same advanced XviD encoding options as above, here’s what a two pass encoding job would look like.
mencoder dvd:// -nosound -passlogfile pass1.log
-ovc xvid -xvidencopts pass=1:turbo:autoaspect:vhq=0:max_key_interval=25
-o /dev/null
mencoder dvd:// -oac mp3lame -lameopts q=0:aq=0 -passlogfile pass1.log
-ovc xvid -xvidencopts pass=2:autoaspect:max_key_interval=25:bitrate=1500:
vhq=2:bvhq=1:trellis:hq_ac:chroma_me:chroma_opt:quant_type=mpeg -o video.avi
Cropping Black Borders
If your video source has black borders, you can crop them out to reduce the overall size of your video. For example, you video may resemble the following diagram.
Video with black borders
These borders can be cropped with a video filter -vf crop=w:h:x:y where w, h, x and y are the width, height, x and y coordinates. To help determine which crop values are appropriate, first play your video with mplayer using the -vf cropdetect option, and seek through the movie to bright points of the movie where the black borders are clearly visible. Dark opening scenes may give you inaccurate edge readings.
mencoder dvd:// -vf cropdetect
(snipped for brevity)
[CROP] Crop area: X: 6..711 Y: 0..575 (-vf crop=704:576:8:0).0 0
[CROP] Crop area: X: 6..711 Y: 0..575 (-vf crop=704:576:8:0).0 0
[CROP] Crop area: X: 6..711 Y: 0..575 (-vf crop=704:576:8:0).0 0
[CROP] Crop area: X: 6..711 Y: 0..575 (-vf crop=704:576:8:0).0 0
[CROP] Crop area: X: 6..711 Y: 0..575 (-vf crop=704:576:8:0).0 0
Copy the values that mplayer displays in the background terminal as the example above shows and use them like the following.
mencoder dvd:// -vf crop=704:576:8:0 (other options)
Conclusion
I hope this post provides you with detail that helps you with your DVD encoding endeavors. Please feel free to post your comments, questions and tips. If needed, I’ll adjust the post to include your valuable input!
Posted by admin on April 9, 2009 under Tech Tips |
I recently wanted to convert some of my 720p and 1080p Matroska Video (MKV) files to the Xvid format so that I can play them on my Xbox 360 (check out ushare). I really wanted to make sure that the video quality and Dolby Digital 5.1 audio would remain intact, and was pleased to get the job done with mencoder.
In the following example, I decided to use a single pass, fixed quantizer value of 4. The audio will simply be copied.
mencoder movie.mkv -channels 6 -ovc xvid -xvidencopts fixed_quant=4 \
-vf harddup -oac copy -o movie.avi
The Dolby Digital 5.1 (AC3) output was a major pain to figure out because by default, mencoder (and mplayer) only will select 2 audio channels. So increasing the value to 6 ensures you receive them all. Otherwise, you end up getting standard stereo out all channels.
There’s a ton of options that you can use, so just be sure to read the man pages for mencoder.
NOTE 1: This is not an exhaustive or definitive post on quality retention. This is just an easy way to re-encode a source video file to Xvid.
NOTE 2: MKV is only a container file format, meaning that you store audio and video tracks within an MKV file, as well as a number of other data types. e.g. Subtitles, Pictures, Fonts, etc. Many times, these video and audio tracks may already have been encoded with a codec supported by your media player. You could potentially extract the appropriate audio and video tracks with mkvextract (a component of the mkvtoolnix package), and recombine them into a container format supported by your platform. This is a great option because you would not have to re-encode, saving time and quality loss. I’ll update with more examples later.
