How to use ffmpeg to add a text to avi video?

Question

I am trying to put a simple text on the bottom of video using ffmpeg on Ubuntu 12.04 . I tried this which is suggested in several places:

ffmpeg -i input.avi -vf drawtext="fontfile=/usr/share/fonts/truetype/ttf-dejavu/DejaVuSerif.ttf:text='Text to write':fontsize=20:fontcolor=black:x=100:y=100" output.avi

But I get this error each time:

ffmpeg version 0.8.3-4:0.8.3-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the Libav developers
  built on Jun 12 2012 16:37:58 with gcc 4.6.3
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
Input #0, avi, from 'input.avi':
  Duration: 04:09:09.66, start: 0.000000, bitrate: 480 kb/s
    Stream #0.0: Video: mpeg4 (Advanced Simple Profile), yuv420p, 320x240 [PAR 1:1 DAR 4:3], 45 tbr, 45 tbn, 45 tbc
    Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 64 kb/s
[buffer @ 0x860d5a0] w:320 h:240 pixfmt:yuv420p
Incompatible sample format 's16' for codec 'ac3', auto-selecting format 'flt'
[ac3 @ 0x8607a00] invalid bit rate
Output #0, avi, to 'output.avi':
    Stream #0.0: Video: mpeg4, yuv420p, 320x240 [PAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 90k tbn, 45 tbc
    Stream #0.1: Audio: ac3, 48000 Hz, stereo, flt, 200 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1
Error while opening encoder for output stream #0.1 - maybe incorrect parameters such as bit_rate, rate, width or height

Appreciate your help.

Solution

The documentation shows that you can use other parameters with x or y such as input video height and width and text width and height. To place the text on the bottom one method is y=main_h-text_h. If you want a little padding on the bottom you can use y=main_h-(text_h*2) To center it horizontally use x=(main_w/2-text_w/2).