[FFmpeg-user] unable to capture desktop session using x11grab on debian jessie with ffmpeg 3.1.4

[Andy Furniss]

肖文良 wrote:
> Built from the latest git source seems not help.
>
> following command runs about 15+ seconds. nothing was captured. If I add -loglevel debug,  this log keep being printed:
>
> cur_dts is invalid (this is harmless if it occurs once at the start per stream)
> [rawvideo @ 0x3234840] PACKET SIZE: 4196352, STRIDE: 5464
>
> Here is the whole command line and output:
>
> ➜  ffmpeg git:(master) ✗ ./ffmpeg  -s 1366x768 -f x11grab -i :0.0 -c libx264 -crf 28 -preset ultrafast /tmp/output.mp4
> ffmpeg version N-82294-g6f0a171 Copyright (c) 2000-2016 the FFmpeg developers
>    built with gcc 4.9.2 (Debian 4.9.2-10)
>    configuration: --disable-yasm --enable-x11grab --enable-gpl --enable-libx264

I would install yasm and remove --disable-yasm it can make a lot of 
difference perf wise.

>    libavutil      55. 35.100 / 55. 35.100
>    libavcodec     57. 66.101 / 57. 66.101
>    libavformat    57. 57.100 / 57. 57.100
>    libavdevice    57.  2.100 / 57.  2.100
>    libavfilter     6. 66.100 /  6. 66.100
>    libswscale      4.  3.100 /  4.  3.100
>    libswresample   2.  4.100 /  2.  4.100
>    libpostproc    54.  2.100 / 54.  2.100
> [x11grab @ 0x363f4e0] Stream #0: not enough frames to estimate rate; consider increasing probesize
> Input #0, x11grab, from ':0.0':
>    Duration: N/A, bitrate: N/A
>      Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1366x768, 29.97 fps, 1000k tbr, 1000k tbn, 1000k tbc
> File '/tmp/output.mp4' already exists. Overwrite ? [y/N] y
> No pixel format specified, yuv444p for H.264 encoding chosen.

Using libx264rgb will give better quality (but bigger files) than 444.
It also avoids the conversion to 444 which saves some CPU load.
If you need to make "normal" files you could recode to 420 later.

> Use -pix_fmt yuv420p for compatibility with outdated media players.
> [libx264 @ 0x3649060] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX AVX2 FMA3 LZCNT BMI2
> [libx264 @ 0x3649060] profile High 4:4:4 Predictive, level 3.2, 4:4:4 8-bit
> [libx264 @ 0x3649060] 264 - core 142 r2431 a5831aa - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=6 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=0 intra_refresh=0 rc=crf mbtree=0 crf=28.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0
> Output #0, mp4, to '/tmp/output.mp4':
>    Metadata:
>      encoder         : Lavf57.57.100
>      Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv444p, 1366x768, q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc
>      Metadata:
>        encoder         : Lavc57.66.101 libx264
>      Side data:
>        cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
> Stream mapping:
>    Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
> Press [q] to stop, [?] for help
> [swscaler @ 0x3655080] Warning: data is not aligned! This can lead to a speedloss
> frame=    3 fps=0.1 q=-1.0 Lsize=     335kB time=00:00:00.06 bitrate=41099.8kbits/s dup=0 drop=464 speed=0.0024x

I can't reproduce this, if I make my self too slow for your command 
(--disable-yasm)
I get dups rather than drops. Maybe something else is going on, or you 
are way too slow.