ffmpeg save images with frame type

Question

I'm trying to get the frames of a video file as images, together with tags that if the frame is a I, P or B frame.

I know that ffmpeg can output only a specific type of frame using select

For I-Frames one can do: ffmpeg -i input.mp4 -vf "select='eq(pict_type,PICT_TYPE_I)'" -vsync vfr iframe_%04d.png

Other pict types can be used for B or P frames. However this will output the frames as iframe_0001.png, iframe_0002.png, etc. The original frame number in the video is lost.

For example, to achieve something like: iframes_0001.png, bframe_0002.png, bframe_0003.png, pframe_0004.png, bframe_0005.png, iframe_0006.png, ...

It's ok if several passes are required, it's also ok to generate an auxiliary file that specifies the type of frame it is (maybe a text file with frame number and frame properties).

Answer 1

Use

ffmpeg -i input.mp4 -filter_complex "setpts=N/TB,select='1*eq(pict_type,PICT_TYPE_I)+2*eq(pict_type,PICT_TYPE_P)+3*eq(pict_type,PICT_TYPE_B)':n=3[i][p][b]" -vsync 0 -map "[i]" -r 1 -frame_pts 1 iframe_%04d.png -map "[p]" -r 1 -frame_pts 1 pframe_%04d.png -map "[b]" -r 1 -frame_pts 1 bframe_%04d.png

The select filter can generate multiple outputs at once. Which output a frame is sent to, depends on the evaluated value of the expression. The expression above will evaluate to either 1, 2 or 3 depending on the frame type and get sent to the first, second or third output respectively. These three outputs are then mapped to different outputs.

The frame_pts option makes the filenames contain the frame timestamp. Before the select filter, setpts filter is added to make the frame timestamps 1 second apart. -r 1 is added to each output so that the filenames are as expected. See Extract I-frames to images quickly for why.