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Encoding Video for the Android Phone, for example, G1

Google G1 phone can decode mpeg4, h263 and h264 codecs and can play mp4 and 3gp video formats. Since these format combinations are relatively uncommon, here are instructions to convert your videos to the compatible format.

Before you begin

Fixing ffmpeg on Ubuntu

For most versions of Ubuntu, ffmpeg in Medibuntu contains this "unlocked" ffmpeg. Enable Medibuntu with the instructions here.

Starting with video size

G1 phone displays best videos with resolution of 480x320. This is often called 3:2 aspect ratio. The problem is nearly no videos come in this format. Most popular aspect ratios are 4:3 and 16:9, and they will look stretched and deformed unless you pad them properly. So, there are a few more options you'll need to know, but you have to do the math.

  • -padtop #, -padbottom #, -padleft #, -padright # - number of pixels thick of padding (black bar) to put on this edge of the video.

I'll use The Terminal starring Catherine Zeta Jones and Tom Hanks as a perfect example. The rip I have is 480x256. Not the highest grade to begin with, but I'll live. This is a 1.875:1 ratio, neither 16:9, 16:10. 4:3, nor 3:2. Doesn't matter though, because the G1 screen is 480 pixels wide to begin with. We just need to pad the video out to 320 pixels tall. 320 - 256 is 64, so we need 32 pixels top and bottom: -padtop 32 -padbottom 32 mplayer spits out the size of the movie in the command line window before playing it, so get the size ratios from that. Divide the actual width by the intended width to get a number, then divide the actual height by that same number to get the intended height. This way, your video will always be full width (assuming you're doing widescreen). If you're doing 4:3, simply swap height and width and solve for the other). For another example, Office Space, in my rip, is 672 by 352. I want to scale it to fit 480 by 320. 672 (starting width) divided by 480 (target width) is 1.4, so if I divide 672 by 1.4 I get 480. 1.4 is the magic ratio, because now I know what to divide the starting height by to get the target height. So likewise, I divide 352 (starting height) by 1.4 and I get 251.4 (target height). Since ffmpeg requires an even number (and you can't have a fraction of a pixel), I'll round it down to 250 (252 would work too, it won't be visibly noticeable). So the output video will be 480 by 250. [edit: This is the -s option above, and thus should be -s 480x250 on the ffmpeg command line.] This will be full width in the G1, but requires padding top and bottom to prevent the G1 decoder from stretching it to fill the screen. 320 (screen height) - 250 (video height) is 70. Since the padding number must be an even one, I'll go with 34 pixels on top and 36 on the bottom to equal 70 total. (edit: -padtop 34 -padbottom 36 on the ffmpeg command line.) But what if you like old T.V. shows, videos from your digital camera or a camcoder? Let's say we have a 4:3 video, let's say it's 640 by 480, and we want it to be on the G1. Well, if we fit full width, the G1 will shrink it to fit, and everyone will look wide, so instead, we fit it full height and pad out the width. We know, therefore, the height has to be 320, but it's currently 480. 480 divided by 320 is 1.5, so we divide 640 by 1.5 to get the intended width of 426.667. So we can scale 640x480 down to 426x320. It will now need padding on the left and right to keep G1 from stretching it out to fit the screen. 480 wide, minus 426 output, is 54. Divide by 2 to get 27. Pad left 26 and pad right 28 and you'll have perfect aspect ratio that will fit the screen. The size and the padding options apply to the following two sections. The -s is the output size BEFORE applying crop and pad arguments. The padding options will be used in examples below.

MPEG4 (standard) encoding

The default encoding of the videos is MPEG-4 ASP (i.e. "xvid") format video using ffmpeg's mpeg4 encoder. If you are interested in higher quality encodings, which will take quite a bit more time but may result in better quality, see H.264 section below. To convert a file source-video.avi to a desired G1 format, run the following command: 

ffmpeg -i source-video.avi -s 480x320 -vcodec mpeg4 -acodec aac -ac 1 -ar 16000 -r 13 -ab 32000 -aspect 3:2 output-video.G1.mp4

This is VERY basic. For full options, go to FFmpeg Documentation

  • -s is "size" of output video. This gave me fits early on because I tried it before (via GUI wrappers, IIRC) and was told by the program that this size wasn't supported regardless of which codec I selected. I don't know what the diff is, but it works for me now.
  • -vcodec Choices for G1 are mpeg4 and h263. IMHO I get better quality and marginally smaller file size with mpeg4.
  • -acodec aac is the audio codec. I know of no other choice here for this purpose.
  • Older versions of ffmpeg called this option -acodec libfaac.
  • -ac 1 Number of audio channels. Use 1 to save filesize since you only have one speaker. Unless you like wearing those painful earbuds all the time. Then use -ac 2.
  • -ar 16000 Audio sampling rate in Hertz. Some formats won't work with anything other than 8kHz. 16 kHz seems okay to me, considering what I'm watching it on. Don't expect !HiFi from a phone.
  • -r 13 Frames per second. Larger is smoother, but 30 fps requires double the file size of 15 fps. 12 is about the slowest my eyes can comfortably watch. Since DVDs are right at 25 FPS, 12.5 being half of this, I go with 13. My camera makes 30 FPS; in that case, use -r 15.
  • -ab 32000 bitrate of the audio -- 32 kbps in this case. Normally I'd balk at such low numbers, but remember, I'm trying to keep filesize low. I'm not broadcasting to a large audience with this, am I? No, it's for me. For you? Use your best judgement. Experiment a little.
  • -aspect 3:2 Obviously, this is the aspect ratio of the output file. I'm not sure it matters, when the output size is being set before.

With padding suggested above, the command line would be: 

ffmpeg -i terminal.avi -s 480x256 -vcodec mpeg4 -acodec aac -ac 1 -ar 16000 -r 13 -ab 32000 -aspect 3:2 -padtop 32 -padbottom 32 terminal.G1.mp4

While ffmpeg is running, you should see the following: 

Output #0, mp4, to 'terminal.G1.mp4':
   Stream #0.0: Video: mpeg4, yuv420p, 480x320 [PAR 1:1 DAR 3:2], q=2-31, 200 kb/s, 13.00 tb(c)
   Stream #0.1: Audio: aac, 16000 Hz, mono, s16, 32 kb/s

This will tell you exactly what the output file will be in width and height, and for the G1 should always be 480x320 for optimum scaling. If it's anything other than 480 by 320, you WILL have stretching in the playback on the G1. May be minimal; may not even be noticeable, but it will be there.

H.264 Encoding

H.264 (MPEG-4 AVC) is a newer codec that the G1 supports. It's able to deliver similar quality at half the bitrate of MPEG-4 ASP! However, it is an extremely slow and CPU-intensive encoder. Expect the encode to take 5x longer than mpeg4 or xvid. You also need ffmpeg with x264 support. Due to the G1's limited feature support for H.264, the command for doing the encode is that much more complex. If you are interested in technical details, G1 supports only the BP (Baseline Profile) dialect of H.264; videos that use more advanced features of H.264 play incorrectly, or not at all. In case of incorrect video encoding, the most typical error is a black screen during playback on G1 while the audio plays. Note that since we am striving for better quality, the audio encoding is also set to higher standards. Assuming source movie has aspect ratio 3:2, the command is: 

ffmpeg -i source-video.avi -s 480x320 -b 384k -vcodec h264 -flags +loop+mv4 -cmp 256 -partitions +parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 -subq 7 -trellis 1 -refs 5 -bf 0 -flags2 +mixed_refs -coder 0 -me_range 16 -g 250 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -qmin 10 -qmax 51 -qdiff 4 -acodec aac -r 13 output-video.G1.mp4

For example of a typical American camcoder which records at 640x480 resolution with 30 frames per second rate, we will add the padding and change the rate (-r 15) as discussed in the previous sections: 

ffmpeg -i myparty.avi -s 426x320 -b 384k -vcodec h264 -flags +loop+mv4 -cmp 256 -partitions +parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 -subq 7 -trellis 1 -refs 5 -bf 0 -flags2 +mixed_refs -coder 0 -me_range 16 -g 250 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -qmin 10 -qmax 51 -qdiff 4 -acodec aac -r 15 -padleft 28 -padright 26 myparty.G1.mp4

While ffmpeg is running, you should see the following: 

Output #0, mp4, to 'myparty.G1.mp4':
  Stream #0.0: Video: h264, yuv420p, 480x320, q=10-51, 384 kb/s, 15.00 fps(c)
  Stream #0.1: Audio: aac, 44100 Hz, stereo, 64 kb/s

This will tell you exactly what the output file will be in width and height, and for the G1 should always be 480x320 for optimum scaling. If it's anything other than 480 by 320, you WILL have stretching in the playback on the G1. May be minimal; may not even be noticeable, but it will be there.

GUI version (using WinFF)

Install WinFF using the following instructions (Reposted -- Updated instructions may be available)

Video Conversion

For video conversion and editing capabilities, you will first need to add a new repository to your software sources, as it will enable you to install the very useful WinFF, which is a GUI front-end for the command-line video conversion tool, FFmpeg. The command I want you to copy and paste for adding the actual repository is intended for Ubuntu 8.10 Intrepid Ibex, so if you're using a different version of Ubuntu, you will need to edit the "intrepid" part accordingly, then move the cursor back to where it was before executing the edited command. Copy and paste the following command into the terminal to add the new WinFF repository (EXAMPLE FOR INTREPID, SUBSTITUTE WITH YOUR VERSION): 

echo "deb http://winff.org/ubuntu intrepid universe" | sudo tee /etc/apt/sources.list.d/winff.list

This second command will merely install something called a GPG Key, so will not need editing by anyone: 

wget --quiet --output-document=- "http://winff.org/ubuntu/AAFE086A.gpg" | sudo apt-key add - && sudo apt-get update

Finally, execute the command below to install the applications needed for video conversion and editing: 

sudo apt-get install avidemux ffmpeg winff

WinFF is probably the most user-friendly tool for converting videos and extracting audio from videos in GNU/Linux. Avidemux is a popular and useful video editing application, which makes it quite simple to cut and crop videos to your liking, and much more.

G1-specific Video Conversion Instructions

模板:Http://winff.org/images/screenshots/winff044-ubuntu-small.jpg

  • Click on Options and verify that Additional Options are selected -- they will show up on the bottom of the screen
  • Click on Add and select one or multiple movies that you want to convert.
  • Select Convert to: Ipod
  • Select Device Presets: H.264 for Ipod *Linux* (4:3) for standard resolution or H.264 for Ipod *Linux* (16:9) for wide resolution
  • In the Additional Options below, choose Video Settings and type Video Size: 432 x 320 for standard resolution and 480 x 272 for wide resolution
  • In Audio Settings: If you are planning to listen primarily with headphones, do nothing. If you are planning to listen on the speakerphone, select Audio Channels: 1 to create mono sound.
  • Click on Convert toolbar icon.

Get help

As always, Ubuntuforums is a great place to ask for help. Please use the Multimedia Production category.

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Additional information

取自“https://wiki.ubuntu.org.cn/index.php?title=UbuntuHelp:AndroidVideoEncoding&oldid=121576”