user17670: The scene: Ubuntu 16.04, newly upgraded from 14.04 where things perked along happily with avconv
The props: a directory full of stills, motor_animate_000.gif, motor_animate_001.gif, etc.
The players: Me, a mostly-newbie ffmpeg user, and ffmpeg.
The drama:
Based on a suggestion I had to solve another problem, I execute the command line:
ffmpeg -f image2 -framerate 30 -i motor_animate_%03d.gif motor.mpg
After the usual excrutiating detailed list of stuff from ffmpeg, I get the following error message (in more than one color, ooh, ooh).
[image2 @ 0x14f8420] Could not find codec parameters for stream 0 (Video: none, none): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
motor_animate_%03d.gif: could not find codec parameters
Input #0, image2, from 'motor_animate_%03d.gif':
  Duration: 00:00:04.03, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: none, none, 30 fps, 30 tbr, 30 tbn, 30 tbc
File 'motor.mpg' already exists. Overwrite ? [y/N] y
No decoder for stream #0:0, filtering impossible
Error opening filters!
Can anyone tell me what's going on and how to fix it?  All I want to do is make an mpeg clip out of a bunch of one-frame gifs.
Thanks.

user1871: It's worth a try using the concat demuxer.
First, create a text file like this:
file 'motor_animate_000.gif'
file 'motor_animate_001.gif'
file 'motor_animate_002.gif'
file 'motor_animate_003.gif'
...

Then run
ffmpeg -f concat -i list.txt motor.mpg

Do note that by just specifying a .MPG filename as output parameter, ffmpeg will encode to MPEG-1 at a bitrate of 200 kb/s. If MP4 is not acceptable and .mpg is needed, then add -c:v mpeg2video -b:v 1000k after list.txt to set codec and avg. bitrate. For MP4, just change extension; the defaults are decent.

17670: <p>The scene: Ubuntu 16.04, newly upgraded from 14.04 where things perked along happily with avconv</p>

<p>The props: a directory full of stills, motor_animate_000.gif, motor_animate_001.gif, etc.</p>

<p>The players: Me, a mostly-newbie ffmpeg user, and ffmpeg.</p>

<p>The drama:</p>

<p>Based on a suggestion I had to solve another problem, I execute the command line:</p>

<p>ffmpeg -f image2 -framerate 30 -i motor_animate_%03d.gif motor.mpg</p>

<p>After the usual excrutiating detailed list of stuff from ffmpeg, I get the following error message (in more than one color, ooh, ooh).</p>

<p>[image2 @ 0x14f8420] Could not find codec parameters for stream 0 (Video: none, none): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
motor_animate_%03d.gif: could not find codec parameters
Input #0, image2, from 'motor_animate_%03d.gif':
  Duration: 00:00:04.03, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: none, none, 30 fps, 30 tbr, 30 tbn, 30 tbc
File 'motor.mpg' already exists. Overwrite ? [y/N] y
No decoder for stream #0:0, filtering impossible
Error opening filters!</p>

<p>Can anyone tell me what's going on and how to fix it?  All I want to do is make an mpeg clip out of a bunch of one-frame gifs.</p>

<p>Thanks.</p>
 1871: <p>It's worth a try using the concat demuxer.</p>

<p>First, create a text file like this:</p>

<pre><code>file 'motor_animate_000.gif'
file 'motor_animate_001.gif'
file 'motor_animate_002.gif'
file 'motor_animate_003.gif'
...
</code></pre>

<p>Then run</p>

<pre><code>ffmpeg -f concat -i list.txt motor.mpg
</code></pre>

<p>Do note that by just specifying a <code>.MPG</code> filename as output parameter, ffmpeg will encode to MPEG-1 at a bitrate of 200 kb/s. If MP4 is not acceptable and .mpg is needed, then add <code>-c:v mpeg2video -b:v 1000k</code> after <code>list.txt</code> to set codec and avg. bitrate. For MP4, just change extension; the defaults are decent.</p>
