FFmpeg/FFprobe marks non-idr keyframes as keyframes

Question

I have a video clip I want to get the positions of all keyframes from. To achieve this, I tried running various ffmpeg/ffprobe commands, but all of them return similar output. From first 20 seconds of the video I always get keyframes at:

frame,0.000000
frame,3.000000
frame,5.000000
frame,6.416667
frame,10.000000
frame,15.000000
frame,19.041667

All of those also have the is_key value set to 1. The problem is, that the 'real' keyframes are only at intervals of 5. So of those above, the working keyframes are:

frame,0.000000
frame,5.000000
frame,10.000000
frame,15.000000

but if I try actually using other ones to, for instance, -c copy a part of video out, ffmpeg actually skips the non-idr keyframes and copies from previous keyframe to the point I requested.

Also in Avidemux if I load the file into it, the option 'jump to next/previous keyframe' only jumps between the keyframes at interval of 5.

How can I get ffmpeg/ffprobe to only return information about the usable keyframes, without knowing the file beforehand?

link to the file I worked on (it's big, but it's the only one I have right now)

https://drive.google.com/open?id=1aV3BLCrxNMhZX4uSBJzoiuNUhSm9CFap

full log output

ffprobe -loglevev verbose -skip_frame nokey -select_streams v -show_entries frame=key_frame,pkt_pts_time -of" csv=print_section=1 -read_intervals 0%+20 srcFile.mp4

ffprobe version n4.0-39-gda39990 Copyright (c) 2007-2018 the FFmpeg developers
  built with gcc 4.9.x (GCC) 20150123 (prerelease)
  configuration: --target-os=linux --cross-prefix=/root/bravobit/ffmpeg-android/toolchain-android/bin/arm-linux-androideabi- --arch=arm --cpu=cortex-a8 --enable-runtime-cpudetect --sysroot=/root/bravobit/ffmpeg-android/toolchain-android/sysroot --enable-pic --enable-libx264 --enable-ffprobe --enable-libopus --enable-libvorbis --enable-libfdk-aac --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-fontconfig --enable-libvpx --enable-libass --enable-yasm --enable-pthreads --disable-debug --enable-version3 --enable-hardcoded-tables --disable-ffplay --disable-linux-perf --disable-doc --disable-shared --enable-static --enable-runtime-cpudetect --enable-nonfree --enable-network --enable-avresample --enable-avformat --enable-avcodec --enable-indev=lavfi --enable-hwaccels --enable-ffmpeg --enable-zlib --enable-gpl --enable-small --enable-nonfree --pkg-config=pkg-config --pkg-config-flags=--static --prefix=/root/bravobit/ffmpeg-android/build/armeabi-v7a --extra-cflags='-I/root/bravobit/ffmpeg-android/toolchain-android/include -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fno-strict-overflow -fstack-protector-all' --extra-ldflags='-L/root/bravobit/ffmpeg-android/toolchain-android/lib -Wl,-z,relro -Wl,-z,now -pie' --extra-cxxflags=
  libavutil      56. 14.100 / 56. 14.100
  libavcodec     58. 18.100 / 58. 18.100
  libavformat    58. 12.100 / 58. 12.100
  libavdevice    58.  3.100 / 58.  3.100
  libavfilter     7. 16.100 /  7. 16.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  1.100 /  5.  1.100
  libswresample   3.  1.100 /  3.  1.100
  libpostproc    55.  1.100 / 55.  1.100
Adding 'key_frame' to the entries to show in section 'frame'
Adding 'pkt_pts_time' to the entries to show in section 'frame'
Parsed log interval id:0 start:0 end:+20
[h264 @ 0xe9fa9380] Reinit context to 1280x720, pix_fmt: yuv420p
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/storage/emulated/0/Movies/Capture/bobross.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2016-08-22T05:06:42.000000Z
  Duration: 10:00:27.90, start: 0.000000, bitrate: 1127 kb/s
    Stream #0:0(und): Video: h264, 1 reference frame (avc1 / 0x31637661), yuv420p(left), 1280x720 [SAR 1:1 DAR 16:9], 997 kb/s, 24 fps, 24 tbr, 90k tbn, 48 tbc (default)
    Metadata:
      creation_time   : 2016-08-22T05:06:42.000000Z
      handler_name    : ISO Media file produced by Google Inc.
    Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 125 kb/s (default)
    Metadata:
      creation_time   : 2016-08-22T05:06:42.000000Z
      handler_name    : ISO Media file produced by Google Inc.
Processing read interval id:0 start:0 end:+20
Seeking to read interval start point 0
[h264 @ 0xe9fa9e00] Reinit context to 1280x720, pix_fmt: yuv420p
ffprobe version n4.0-39-gda39990 Copyright (c) 2007-2018 the FFmpeg developers
  built with gcc 4.9.x (GCC) 20150123 (prerelease)
  configuration: --target-os=linux --cross-prefix=/root/bravobit/ffmpeg-android/toolchain-android/bin/arm-linux-androideabi- --arch=arm --cpu=cortex-a8 --enable-runtime-cpudetect --sysroot=/root/bravobit/ffmpeg-android/toolchain-android/sysroot --enable-pic --enable-libx264 --enable-ffprobe --enable-libopus --enable-libvorbis --enable-libfdk-aac --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-fontconfig --enable-libvpx --enable-libass --enable-yasm --enable-pthreads --disable-debug --enable-version3 --enable-hardcoded-tables --disable-ffplay --disable-linux-perf --disable-doc --disable-shared --enable-static --enable-runtime-cpudetect --enable-nonfree --enable-network --enable-avresample --enable-avformat --enable-avcodec --enable-indev=lavfi --enable-hwaccels --enable-ffmpeg --enable-zlib --enable-gpl --enable-small --enable-nonfree --pkg-config=pkg-config --pkg-config-flags=--static --prefix=/root/bravobit/ffmpeg-android/build/armeabi-v7a --extra-cflags='-I/root/bravobit/ffmpeg-android/toolchain-android/include -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fno-strict-overflow -fstack-protector-all' --extra-ldflags='-L/root/bravobit/ffmpeg-android/toolchain-android/lib -Wl,-z,relro -Wl,-z,now -pie' --extra-cxxflags=
  libavutil      56. 14.100 / 56. 14.100
  libavcodec     58. 18.100 / 58. 18.100
  libavformat    58. 12.100 / 58. 12.100
  libavdevice    58.  3.100 / 58.  3.100
  libavfilter     7. 16.100 /  7. 16.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  1.100 /  5.  1.100
  libswresample   3.  1.100 /  3.  1.100
  libpostproc    55.  1.100 / 55.  1.100
Adding 'key_frame' to the entries to show in section 'frame'
Adding 'pkt_pts_time' to the entries to show in section 'frame'
Parsed log interval id:0 start:0 end:+20
[h264 @ 0xe9fa9380] Reinit context to 1280x720, pix_fmt: yuv420p
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/storage/emulated/0/Movies/Capture/bobross.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2016-08-22T05:06:42.000000Z
  Duration: 10:00:27.90, start: 0.000000, bitrate: 1127 kb/s
    Stream #0:0(und): Video: h264, 1 reference frame (avc1 / 0x31637661), yuv420p(left), 1280x720 [SAR 1:1 DAR 16:9], 997 kb/s, 24 fps, 24 tbr, 90k tbn, 48 tbc (default)
    Metadata:
      creation_time   : 2016-08-22T05:06:42.000000Z
      handler_name    : ISO Media file produced by Google Inc.
    Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 125 kb/s (default)
    Metadata:
      creation_time   : 2016-08-22T05:06:42.000000Z
      handler_name    : ISO Media file produced by Google Inc.
Processing read interval id:0 start:0 end:+20
Seeking to read interval start point 0
[h264 @ 0xe9fa9e00] Reinit context to 1280x720, pix_fmt: yuv420p
frame,1,0.000000frame,1,3.000000frame,1,5.000000frame,1,6.416667frame,1,10.000000frame,1,15.000000frame,1,19.041667

Answer 1

The decoder is marking recovery points as keyframes

e.g. take the frame with PTS 3.00s

This is a recovery point* and the packet contains an I-slice (slice_type 7). Furthermore, as recovery_frame_cnt is 0, the decoder can immediately display frames from this point onwards.

Packet: 25021 bytes, pts 270000, dts 266250, duration 3750.
Supplemental Enhancement Information
0           forbidden_zero_bit                                          0 = 0
1           nal_ref_idc                                                00 = 0
3           nal_unit_type                                           00110 = 6
8           last_payload_type_byte                               00000110 = 6
16          last_payload_size_byte                               00000001 = 1
Recovery Point
24          recovery_frame_cnt                                          1 = 0
25          exact_match_flag                                            1 = 1
26          broken_link_flag                                            0 = 0
27          changing_slice_group_idc                                   00 = 0
29          bit_equal_to_one                                            1 = 1
30          bit_equal_to_zero                                           0 = 0
31          bit_equal_to_zero                                           0 = 0
32          rbsp_stop_one_bit                                           1 = 1
33          rbsp_alignment_zero_bit                                     0 = 0
34          rbsp_alignment_zero_bit                                     0 = 0
35          rbsp_alignment_zero_bit                                     0 = 0
36          rbsp_alignment_zero_bit                                     0 = 0
37          rbsp_alignment_zero_bit                                     0 = 0
38          rbsp_alignment_zero_bit                                     0 = 0
39          rbsp_alignment_zero_bit                                     0 = 0
Slice Header
0           forbidden_zero_bit                                          0 = 0
1           nal_ref_idc                                                10 = 2
3           nal_unit_type                                           00001 = 1
8           first_mb_in_slice                                           1 = 0
9           slice_type                                            0001000 = 7
16          pic_parameter_set_id                                        1 = 0
17          frame_num                                                1111 = 15
21          pic_order_cnt_lsb                                       10000 = 16
26          adaptive_ref_pic_marking_mode_flag                          0 = 0
27          slice_qp_delta                                        0001111 = -7
34          disable_deblocking_filter_idc                               1 = 0
35          slice_alpha_c0_offset_div2                                  1 = 0
36          slice_beta_offset_div2                                      1 = 0
37          cabac_alignment_one_bit                                     1 = 1
38          cabac_alignment_one_bit                                     1 = 1
39          cabac_alignment_one_bit                                     1 = 1

*see https://mailman.videolan.org/pipermail/vlc-commits/2010-October/003615.html

---

If your inputs are MP4s, you can examine the packets to get the IDR key status

ffprobe -loglevel verbose -skip_frame nokey -select_streams v -show_entries packet=pts_time,flags -of csv=print_section=1 -read_intervals 0%+20 srcFile.mp4

For the first 6 seconds, this will show only the frames at 0 and 5.

packet,0.000000,K_
...
packet,3.000000,__
...
packet,5.000000,K_