Getting a dark output when converting .exr sequence to .mp4

With the latest version of ffmpeg (version git-2020-03-24):

• start_frame is replaced by start_number
• $04d is replaced by %04d

I had to add the -vcodec argument to have the expected result.

ffmpeg -y -apply_trc iec61966_2_1 -start_number 1 -i input.%04d.exr  -vcodec mpeg4 output.mp4

The EXR decoder has a parameter to assign color transfer characteristics.

For sRGB, it is

ffmpeg -apply_trc iec61966_2_1 -start_number 1100 -i input%04d.exr output.mp4

Other available values are

 bt709                        .D.V.... BT.709
 gamma                        .D.V.... gamma
 gamma22                      .D.V.... BT.470 M
 gamma28                      .D.V.... BT.470 BG
 smpte170m                    .D.V.... SMPTE 170 M
 smpte240m                    .D.V.... SMPTE 240 M
 linear                       .D.V.... Linear
 log                          .D.V.... Log
 log_sqrt                     .D.V.... Log square root
 iec61966_2_4                 .D.V.... IEC 61966-2-4
 bt1361                       .D.V.... BT.1361
 iec61966_2_1                 .D.V.... IEC 61966-2-1
 bt2020_10bit                 .D.V.... BT.2020 - 10 bit
 bt2020_12bit                 .D.V.... BT.2020 - 12 bit
 smpte2084                    .D.V.... SMPTE ST 2084
 smpte428_1                   .D.V.... SMPTE ST 428-1