"Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)" error message

[Mohammed.Bey]

Hello,
I am facing an error when trying to decode HEVC-coded content for some video sequences.
I varied the video resolution as follows:
2160p: decoded successfully
1600p: decoded successfully
1080p: error
720p: error

When I try to decode low resolutions (720p and 1080p), ffmpeg outputs the following error message: "Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)"

Below are the command line and the output.

---

root@linaro-developer:~/vary_resolution/kimono# ffmpeg -vcodec hevc_v4l2m2m -i AMP_D_Hisilicon_3_1080p_fps_25.265 -f null /dev/null
ffmpeg version 4.3 Copyright (c) 2000-2020 the FFmpeg developers

built with gcc 8 (Debian 8.3.0-6)
configuration: --enable-gpl --enable-nonfree --enable-static --disable-shared --enable-pthreads --enable-neon --enable-thumb --enable-optimizations --enable-libv4l2
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
libswscale 5. 7.100 / 5. 7.100
libswresample 3. 7.100 / 3. 7.100
libpostproc 55. 7.100 / 55. 7.100

Input #0, hevc, from 'AMP_D_Hisilicon_3_1080p_fps_25.265':

Duration: N/A, bitrate: N/A

Stream #0:0: Video: hevc (Main), yuv420p(tv), 1920x1080, 25 fps, 25 tbr, 1200k tbn, 25 tbc

[hevc_v4l2m2m @ 0xaaaaf4f323d0] Using device /dev/video1
[hevc_v4l2m2m @ 0xaaaaf4f323d0] driver 'qcom-venus' on card 'Qualcomm Venus video decoder' in mplane mode
[hevc_v4l2m2m @ 0xaaaaf4f323d0] requesting formats: output=HEVC capture=NV12
Stream mapping:

Stream #0:0 -> #0:0 (hevc (hevc_v4l2m2m) -> wrapped_avframe (native))

Press [q] to stop, ? for help
[hevc_v4l2m2m @ 0xaaaaf4f323d0] VIDIOC_G_FMT ioctl

Last message repeated 99 times

Output #0, null, to '/dev/null':

Metadata:

encoder : Lavf58.45.100
Stream #0:0: Video: wrapped_avframe, yuv420p, 1920x1080, q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
Metadata:

encoder : Lavc58.91.100 wrapped_avframe

frame= 0 fps=0.0 q=0.0 Lsize=N/A time=00:00:00.00 bitrate=N/A speed= 0x
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)

---

Best regards

[Andriy Gelman]

• Can you confirm that you applied this patch before decoding the 720p stream?

​https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200509173541.7667-1-andriy.gelman@gmail.com/
And that the patch fixes a seg fault? (this is how I understand the ML thread)

• Please post console output with -loglevel debug option set. Post the log for the case that works and when it doesn't work.

• Did release 3.4.7 ever work when decoding the 720p stream?

• Please check output of dmesg when decoding fails and post the results if they contain error messages from the driver

[Mohammed.Bey]

Replying to taliho:

• Can you confirm that you applied this patch before decoding the 720p stream?

​https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200509173541.7667-1-andriy.gelman@gmail.com/
And that the patch fixes a seg fault? (this is how I understand the ML thread)

Yes. I applied the patch before compiling ffmpeg. I think it works since the error of " free(): double free detected in tcache 2" has disappeared.

• Please post console output with -loglevel debug option set. Post the log for the case that works and when it doesn't work.

Attached are the outputs:

---

"output_loglevel_debug_ffmpeg_4_3_resolution_2160p.txt" file.

---

"output_loglevel_debug_ffmpeg_4_3_resolution_720p.txt" file.

• Did release 3.4.7 ever work when decoding the 720p stream?

No. I re-compiled ffmpeg-3.4.8 (the latest stable version of 3.4).
Attached are the command line and the output: "output_loglevel_debug_ffmpeg_3_4_8_720p.txt" file.

• Please check output of dmesg when decoding fails and post the results if they contain error messages from the driver

"dmesg" output is in the "output_loglevel_debug_ffmpeg_4_3_resolution_720p.txt" attached file.