Invalid NAL unit size for MP4 created from NALU with 3-byte start code (0x000001)

Question

I have a mp4 muxer that works fine when the H264 NALU has the 4-byte start code (0x00000001). I am adapting it to support 3-byte start code (0x000001) but I am stuck with a bug that I am not able to identify. The MP4 generated open in VLC and MediaPlayer but no video is displayed. In VLC statistics shows that it is decoding blocks but stays with 0 frames displayed.

I then ran a error analyzer using ffmpeg (ffmpeg -v error -i myvideo.mp4 -f null - 2>error.log that shows me the following output:

[h264 @ 0x7fa3b5003200] Invalid NAL unit size (158559 > 158558).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (9338 > 9337).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (6582 > 6581).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (8300 > 8299).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (9336 > 9335).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (9422 > 9421).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (10448 > 10447).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (9208 > 9207).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (8776 > 8775).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (11376 > 11375).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (158311 > 158310).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (9164 > 9163).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (7994 > 7993).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (9974 > 9973).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (9282 > 9281).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.
[h264 @ 0x7fa3b5003200] Invalid NAL unit size (9656 > 9655).
[h264 @ 0x7fa3b5003200] Error splitting the input into NAL units.

I am trying to find why it is complaining about 1 byte difference in all mdat boxes. Also, the smaller values (e.g: 158558) are 12 bytes lower than the size written inside the mdat header.

Anyone could help indicate why that error is happening? The same code is working fine to create MP4 with 4-byte NALU start code.

UPDATE: I ran ffprobe and it provides a few more details, more specifically saying that couldn't find the "codec parameters":

$ ffprobe -analyzeduration 2147483647 -probesize 2147483647 -i myvideo.mp4 
ffprobe version 4.3.1 Copyright (c) 2007-2020 the FFmpeg developers
  built with Apple clang version 11.0.3 (clang-1103.0.32.62)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.1 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (147087 > 147086).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (8104 > 8103).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9752 > 9751).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12058 > 12057).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9026 > 9025).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12032 > 12031).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12566 > 12565).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7906 > 7905).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9758 > 9757).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12840 > 12839).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (146771 > 146770).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7708 > 7707).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9524 > 9523).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12230 > 12229).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9080 > 9079).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12164 > 12163).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12650 > 12649).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7916 > 7915).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9736 > 9735).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (13086 > 13085).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (147143 > 147142).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (8218 > 8217).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9908 > 9907).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12450 > 12449).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7806 > 7805).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9598 > 9597).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12692 > 12691).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9782 > 9781).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12930 > 12929).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12750 > 12749).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (146911 > 146910).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (8182 > 8181).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9494 > 9493).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12268 > 12267).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (8898 > 8897).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11946 > 11945).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12622 > 12621).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (8108 > 8107).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9754 > 9753).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12110 > 12109).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (147067 > 147066).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7726 > 7725).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9424 > 9423).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12078 > 12077).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (8976 > 8975).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11686 > 11685).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11940 > 11939).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9274 > 9273).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11950 > 11949).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11702 > 11701).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (147021 > 147020).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7686 > 7685).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9572 > 9571).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11810 > 11809).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11584 > 11583).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9116 > 9115).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11986 > 11985).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11390 > 11389).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9008 > 9007).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11768 > 11767).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (147347 > 147346).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7618 > 7617).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9266 > 9265).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12046 > 12045).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11562 > 11561).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (8898 > 8897).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11672 > 11671).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11458 > 11457).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (8850 > 8849).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11452 > 11451).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (147213 > 147212).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7540 > 7539).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9610 > 9609).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12302 > 12301).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9154 > 9153).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11868 > 11867).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12054 > 12053).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7508 > 7507).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9136 > 9135).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11812 > 11811).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (147089 > 147088).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7800 > 7799).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9482 > 9481).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12244 > 12243).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9198 > 9197).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11962 > 11961).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12386 > 12385).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7618 > 7617).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (8996 > 8995).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11800 > 11799).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (147135 > 147134).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7934 > 7933).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9742 > 9741).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12398 > 12397).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7540 > 7539).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9130 > 9129).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12482 > 12481).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12002 > 12001).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11710 > 11709).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11886 > 11885).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (147303 > 147302).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7620 > 7619).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9316 > 9315).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12138 > 12137).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9056 > 9055).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11968 > 11967).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11942 > 11941).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9072 > 9071).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11546 > 11545).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (11368 > 11367).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (147363 > 147362).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (7578 > 7577).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9466 > 9465).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (12230 > 12229).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[h264 @ 0x7fa85f800e00] Invalid NAL unit size (9248 > 9247).
[h264 @ 0x7fa85f800e00] Error splitting the input into NAL units.
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fa85f000000] decoding for stream 0 failed
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fa85f000000] Could not find codec parameters for stream 0 (Video: h264 (avc1 / 0x31637661), none, 1280x960, 1717 kb/s): unspecified pixel format
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'myvideo.mp4':
  Metadata:
    major_brand     : iso5
    minor_version   : 512
    compatible_brands: iso6mp41
  Duration: 00:00:13.22, start: 0.000000, bitrate: 1726 kb/s
    Stream #0:0(und): Video: h264 (avc1 / 0x31637661), none, 1280x960, 1717 kb/s, 8.70 fps, 9.25 tbr, 90k tbn, 180k tbc (default)
    Metadata:
      handler_name    : VideoHandle

How could somebody possibly debug this without seeing the code? — szatmary, Sep 03 '20 at 18:32
I am not asking to debug. I am asking for guidance of potential issues. As it shows in the log, ffmpeg is complaining about wrong NAL unit size which is different by 1. Maybe someone already faced this issue before and could share what was the issue. — rsc, Sep 03 '20 at 18:43
The issue is you have the wrong size for the NALU. How did it get this way, who knows? You don’t even say how you are creating this bad file. I can write a program to increment the size field on every NALU in an mp4 and get this result, but I dont know how YOU did it. So it’s impossible to help. — szatmary, Sep 04 '20 at 00:56
You have an mp4 muxer with a bug in it. Fix the bug, we can help you do that but not without seeing the source code. There are millions of things that could be wrong. We cant iterate over all of them here. — szatmary, Sep 04 '20 at 00:58
You appear to think that only providing a code fix is helpful, but that is not the case. Sometimes just pointing the direction is enough to help someone to focus on the right part and eventually fix the code. — rsc, Sep 04 '20 at 15:11
For example, you said that I have mp4 muxer with a bug, which appears to be setting a Wrong NALU size. So, that is a start. Can we go more specific? Is the NALU size header (which is what used to be the NALU start code that I ended up replacing with the size) with a number that doesn't match the actual NALU length? Based on ffprobe the difference appears to be 1 byte, but it is not clear if the header with a size 1 byte larger or smaller than the actual contents. — rsc, Sep 04 '20 at 15:19
Also, I can open my generated mp4 file the mp4 analyzers (ISOViewer in Mac and MP4 Inspectors in Windows) without any problem. The analyzers are able to parse all mp4 boxes and checking the mdat payload I didn't see any difference regarding the size described in the NALU header vs the actual NALU size. — rsc, Sep 04 '20 at 15:21
Because your analyzer is not decoding the full NALU. Your comments provided no new information. Even if you posted the file, all I could tell you is the sizes are wrong, and there is a bug in the muxer. I can’t “point you in the right direction” more than I already have. And I ( nor anybody else) can help you debug code without seeing it. There are an infinite number of ways to create this bug. Good luck. — szatmary, Sep 04 '20 at 15:41
I just found something very interesting. After inspecting the data that my muxer was receiving, I noticed that it started with a 3-byte start code but other NALUs inside of the same data was with a 4-byte start code. So, just for test I "corrected" that first 3-byte start code to be a 4-byte and bam, the mp4 generated plays perfectly. I was able to identify that indeed the source video has a 4-byte start code but the code that receives the data stream and sends it to my muxer was dropping the 1st byte of that 4-byte start code (for an unknown reason yet). So, that leads the 2 questions: — rsc, Sep 08 '20 at 23:38
1) Can a video stream be able to use both between 3-byte and 4-byte start code in the same stream? Or does it needs to choose between one of 2 options stay with it for the entire stream? 2) Does the NALU contents store any information regarding the start code length? I.e, Can I just drop the 1st byte of the 4-byte start code (turning it into a 3-byte start code) without any further modification? — rsc, Sep 08 '20 at 23:42
Yes, you can mix 3 and 4 byte. If you read the link I sent you last week you would have known that. Here it is again. https://stackoverflow.com/questions/24884827/possible-locations-for-sequence-picture-parameter-sets-for-h-264-stream — szatmary, Sep 09 '20 at 00:59
I compared the bad generated mp4 with a good one and the only difference is that the good mp4 has the "sample size" of the TRUN box 1 byte larger than the wrong mp4. — rsc, Sep 09 '20 at 00:59

score 2 · Accepted Answer · answered Sep 09 '20 at 04:19

2

The "Invalid NAL unit size" was referring to the Moof->Traf->Trun "sample size" with a value different than the actual mdat payload size (mdat payload = mdat box without the first 8 bytes which are the length and the 'mdat' name).

That was happening due to my muxer receiving the H264 chunk and using that chunk size as the "sample size" instead of calculating the actual mdat payload size. That bug only got visible when the H264 chunks received by my muxer didn't have a 4-byte NALU start code (since I am using 4 bytes for each NALU length size).

answered Sep 09 '20 at 04:19

rsc

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I wonder what is key difference between 3 bytes start code and 4 bytes start code. Is it possible to convert with each other? – uthline Jun 14 '22 at 16:32
Yes, you can convert from one to the other without problem. But I also don't know why would someone choose 3 instead 4 or 4 instead of 3. – rsc Jun 15 '22 at 05:19

Invalid NAL unit size for MP4 created from NALU with 3-byte start code (0x000001)

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