Regression in transcode example

[pszemus]

Summary of the bug:
doc/examples/transcode.c broken since 6.0 release.
Latest (commit: 2244722) build:

doc/examples/transcode https://test-videos.co.uk/vids/bigbuckbunny/mp4/h264/720/Big_Buck_Bunny_720_10s_1MB.mp4 /tmp/ff6.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'https://test-videos.co.uk/vids/bigbuckbunny/mp4/h264/720/Big_Buck_Bunny_720_10s_1MB.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    title           : Big Buck Bunny, Sunflower version
    artist          : Blender Foundation 2008, Janus Bager Kristensen 2013
    composer        : Sacha Goedegebure
    encoder         : Lavf57.63.100
    comment         : Creative Commons Attribution 3.0 - http://bbb3d.renderfarming.net
    genre           : Animation
  Duration: 00:00:10.00, start: 0.000000, bitrate: 775 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 772 kb/s, 30 fps, 30 tbr, 15360 tbn (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
[libx264 @ 0x26b7000] using SAR=1/1
[libx264 @ 0x26b7000] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2 AVX512
[libx264 @ 0x26b7000] profile High, level 3.1, 4:2:0, 8-bit
[libx264 @ 0x26b7000] 264 - core 164 r3106 eaa68fa - H.264/MPEG-4 AVC codec - Copyleft 2003-2023 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to '/tmp/ff6.mp4':
  Stream #0:0: Video: h264, yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 30 tbn
[in @ 0x2a96d80] Invalid time base 0/1
Cannot create buffer source
Error occurred: Invalid argument

Similar error with 6.0 release but works OK with latest 5 release, e.g. 5.1.3:

doc/examples/transcoding https://test-videos.co.uk/vids/bigbuckbunny/mp4/h264/720/Big_Buck_Bunny_720_10s_1MB.mp4 /tmp/ff5.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'https://test-videos.co.uk/vids/bigbuckbunny/mp4/h264/720/Big_Buck_Bunny_720_10s_1MB.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    title           : Big Buck Bunny, Sunflower version
    artist          : Blender Foundation 2008, Janus Bager Kristensen 2013
    composer        : Sacha Goedegebure
    encoder         : Lavf57.63.100
    comment         : Creative Commons Attribution 3.0 - http://bbb3d.renderfarming.net
    genre           : Animation
  Duration: 00:00:10.00, start: 0.000000, bitrate: 775 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 772 kb/s, 30 fps, 30 tbr, 15360 tbn (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
[libx264 @ 0x2883680] using SAR=1/1
[libx264 @ 0x2883680] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2 AVX512
[libx264 @ 0x2883680] profile High, level 3.1, 4:2:0, 8-bit
[libx264 @ 0x2883680] 264 - core 164 r3106 eaa68fa - H.264/MPEG-4 AVC codec - Copyleft 2003-2023 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to '/tmp/ff5.mp4':
  Stream #0:0: Video: h264, yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 30 tbn
Pushing decoded frame to filters
Pulling filtered frame from filters
Encoding frame
[...]
[libx264 @ 0x2883680] frame I:2     Avg QP:18.47  size:187624
[libx264 @ 0x2883680] frame P:75    Avg QP:20.40  size: 31522
[libx264 @ 0x2883680] frame B:221   Avg QP:26.49  size:  2792
[libx264 @ 0x2883680] consecutive B-frames:  1.0%  0.0%  1.0% 98.0%
[libx264 @ 0x2883680] mb I  I16..4:  0.3% 84.2% 15.5%
[libx264 @ 0x2883680] mb P  I16..4:  0.0%  0.1%  0.0%  P16..4: 43.3% 28.6% 20.0%  0.0%  0.0%    skip: 8.0%
[libx264 @ 0x2883680] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8: 52.1%  3.1%  0.4%  direct: 0.3%  skip:44.1%  L0:46.7% L1:46.9% BI: 6.4%
[libx264 @ 0x2883680] 8x8 transform intra:84.0% inter:63.1%
[libx264 @ 0x2883680] coded y,uvDC,uvAC intra: 99.1% 94.2% 76.9% inter: 12.4% 11.0% 0.9%
[libx264 @ 0x2883680] i16 v,h,dc,p:  6% 48%  3% 42%
[libx264 @ 0x2883680] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 10% 11%  9%  9% 13% 12% 13% 11% 13%
[libx264 @ 0x2883680] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 13% 10%  9% 10% 13% 12% 11% 11% 11%
[libx264 @ 0x2883680] i8c dc,h,v,p: 42% 28% 14% 17%
[libx264 @ 0x2883680] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x2883680] ref P L0: 51.8% 19.3% 23.1%  5.9%
[libx264 @ 0x2883680] ref B L0: 82.7% 10.8%  6.4%
[libx264 @ 0x2883680] ref B L1: 90.9%  9.1%
[libx264 @ 0x2883680] kb/s:1351.59

[Jun Zhao]

The commit 5f9e848e686a3c0795939809712b260af5c1adb8 breaks the example

[Elon Musk]

Fixed after ba32f284983037bcf65c8eb372703cd15bc35078