$ ffmpeg -framerate 1 -pattern_type sequence -f image2 -i 'frame-%04d.jpg' -r 1 -s hd720 argh.avi
ffmpeg version 1.2.1 Copyright (c) 2000-2013 the FFmpeg developers
  built on May 18 2013 15:05:37 with Apple LLVM version 4.2 (clang-425.0.28) (based on LLVM 3.2svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/1.2.1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --enable-avresample --enable-vda --cc=cc --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid
  libavutil      52. 18.100 / 52. 18.100
  libavcodec     54. 92.100 / 54. 92.100
  libavformat    54. 63.104 / 54. 63.104
  libavdevice    54.  3.103 / 54.  3.103
  libavfilter     3. 42.103 /  3. 42.103
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
[image2 @ 0x7fd400806600] max_analyze_duration 5000000 reached at 5000000 microseconds
Input #0, image2, from 'frame-%04d.jpg':
  Duration: 01:01:22.00, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: mjpeg, yuvj420p, 1680x1260 [SAR 118:118 DAR 4:3], 1 fps, 1 tbr, 1 tbn, 1 tbc
File 'argh.avi' already exists. Overwrite ? [y/N] y
Output #0, avi, to 'argh.avi':
  Metadata:
    ISFT            : Lavf54.63.104
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 1280x720 [SAR 3:4 DAR 4:3], q=2-31, 200 kb/s, 1 tbn, 1 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg -> mpeg4)
Press [q] to stop, [?] for help
frame= 3682 fps= 46 q=2.0 Lsize=   86574kB time=01:01:22.00 bitrate= 192.6kbits/s
video:86480kB audio:0kB subtitle:0 global headers:0kB muxing overhead 0.109688%