FFMPEG 在使用 rtsp-simple-server 降低 FPS 和通过 RTSP 流式传输时保持质量

Question

我正在使用 rtsp-simple-server ( https://github.com/aler9/rtsp-simple-server ) 并向 RTSP 服务器提供 FFMPEG 流。
我使用 docker compose 文件来启动流:

version: "3.8"

services:

  ffmpeg:
    container_name: ffmpeg-base
    restart: always
    image: "jenssgb/rtspffmpeg:base"
    depends_on:
      - rtsp-server
    volumes:
      - $PWD/:/video
    network_mode: "host"
    command: "ffmpeg -re -stream_loop -1 -i /video/footage-1-b.mp4 -c copy -f rtsp rtsp://localhost:8554/compose-rtsp"
  
  rtsp-server:
    container_name: rtsp-server-base
    restart: always
    image: "aler9/rtsp-simple-server"
    network_mode: "host"

现在我正在尝试通过转码来降低视频的 FPS:

command: -re -stream_loop -1 -i ${VIDEO_FILE} -vf "fps=${FPS_COMPOSE}" -f rtsp rtsp://localhost:8554/compose-rtsp

这基本上是有效的， 但是输出视频的质量变得很差 .我尝试了很多东西，例如 -c:v libx264这确实帮助了一分钟，但让 ffmpeg 崩溃了。

av_interleaved_write_frame(): Broken pipe0:00:09.99 bitrate=N/A speed=0.985x    
[rtsp @ 0x5563b1755640] Packets poorly interleaved, failed to avoid negative timestamp -33660 in stream 0.
Try -max_interleave_delta 0 as a possible workaround.
av_interleaved_write_frame(): Broken pipe
Error writing trailer of rtsp://localhost:8554/compose-rtsp: Broken pipe

知道如何降低 FPS 将流发送到服务器但保持视频质量吗？稍后我也会降低分辨率 - 但现在我想保持分辨率和质量，但只降低 FPS。
我使用 -c:v libx264 进行的测试的完整日志:

    ffmpeg -re -stream_loop -1 -i footage-1-b.mp4 -vf "fps=5" -c:v libx264 -f rtsp rtsp://localhost:8554/compose-rtsp
ffmpeg version 4.2.4-1ubuntu0.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.3.0-10ubuntu2)
  configuration: --prefix=/usr --extra-version=1ubuntu0.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'footage-1-b.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    title           : Session streamed by "nessyMediaServer"
    encoder         : Lavf58.29.100
    comment         : h264_3
  Duration: 00:59:59.63, start: 0.000000, bitrate: 2099 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuvj420p(pc), 1280x720 [SAR 1:1 DAR 16:9], 2061 kb/s, 24.96 fps, 25 tbr, 12800 tbn, 25 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 8000 Hz, mono, fltp, 35 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[aac @ 0x56277bc7f840] Too many bits 8832.000000 > 6144 per frame requested, clamping to max
[libx264 @ 0x56277bbc33c0] using SAR=1/1
[libx264 @ 0x56277bbc33c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x56277bbc33c0] profile High, level 3.1
[libx264 @ 0x56277bbc33c0] 264 - core 155 r2917 0a84d98 - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - 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=5 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, rtsp, to 'rtsp://localhost:8554/compose-rtsp':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    title           : Session streamed by "nessyMediaServer"
    comment         : h264_3
    encoder         : Lavf58.29.100
    Stream #0:0(und): Video: h264 (libx264), yuvj420p(pc), 1280x720 [SAR 1:1 DAR 16:9], q=-1--1, 5 fps, 90k tbn, 5 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      encoder         : Lavc58.54.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
    Stream #0:1(und): Audio: aac (LC), 8000 Hz, mono, fltp, 48 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      encoder         : Lavc58.54.100 aac
av_interleaved_write_frame(): Broken pipe0:00:09.87 bitrate=N/A speed=0.978x    
[rtsp @ 0x56277bba0640] Packets poorly interleaved, failed to avoid negative timestamp -33660 in stream 0.
Try -max_interleave_delta 0 as a possible workaround.
av_interleaved_write_frame(): Broken pipe
Error writing trailer of rtsp://localhost:8554/compose-rtsp: Broken pipe
frame=   50 fps=4.6 q=23.0 Lsize=N/A time=00:00:10.21 bitrate=N/A speed=0.947x    
video:162kB audio:8kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
[libx264 @ 0x56277bbc33c0] frame I:1     Avg QP:19.85  size:165667
[libx264 @ 0x56277bbc33c0] frame P:13    Avg QP:20.88  size:140481
[libx264 @ 0x56277bbc33c0] frame B:36    Avg QP:24.58  size: 55445
[libx264 @ 0x56277bbc33c0] consecutive B-frames:  4.0%  0.0%  0.0% 96.0%
[libx264 @ 0x56277bbc33c0] mb I  I16..4:  4.4% 30.8% 64.8%
[libx264 @ 0x56277bbc33c0] mb P  I16..4:  4.1% 10.6% 20.0%  P16..4: 24.4% 24.8% 13.3%  0.0%  0.0%    skip: 2.6%
[libx264 @ 0x56277bbc33c0] mb B  I16..4:  0.8%  2.0%  4.0%  B16..8: 40.3% 14.5%  5.2%  direct:11.8%  skip:21.4%  L0:77.1% L1: 7.9% BI:14.9%
[libx264 @ 0x56277bbc33c0] 8x8 transform intra:30.1% inter:11.9%
[libx264 @ 0x56277bbc33c0] coded y,uvDC,uvAC intra: 82.5% 60.9% 26.6% inter: 55.0% 42.4% 2.7%
[libx264 @ 0x56277bbc33c0] i16 v,h,dc,p: 17% 26% 34% 23%
[libx264 @ 0x56277bbc33c0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 22% 33% 15%  3%  4%  5%  4%  3%  9%
[libx264 @ 0x56277bbc33c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 20% 22% 13%  3% 17% 11%  5%  3%  6%
[libx264 @ 0x56277bbc33c0] i8c dc,h,v,p: 54% 25% 16%  5%
[libx264 @ 0x56277bbc33c0] Weighted P-Frames: Y:7.7% UV:7.7%
[libx264 @ 0x56277bbc33c0] ref P L0: 33.2% 11.6% 29.0% 23.9%  2.4%
[libx264 @ 0x56277bbc33c0] ref B L0: 79.6% 11.9%  8.5%
[libx264 @ 0x56277bbc33c0] ref B L1: 95.9%  4.1%
[libx264 @ 0x56277bbc33c0] kb/s:3190.34
[aac @ 0x56277bc7f840] Qavg: 65536.000
Conversion failed!

谢谢，
Ĵ

Answer 1

当您说“视频质量变得非常糟糕”时，我猜您的意思是您的转码输出视频中有很多 block 伪影。这通常是因为您没有为输出视频流分配足够的带宽。没有足够的输出带宽可供使用，编码器会量化并消除高频内容，因此看起来很讨厌。
你没有提到你有什么样的节目 Material 。但值得一提的是:在具有大量运动的 Material 中(想想詹姆斯邦德电影)，它不会节省太多带宽来降低帧速率:我们正在编码连续帧之间的差异。您在帧之间等待的时间越长，编码的差异就越大(运动估计器的工作就越困难)。如果您从根本上降低帧速率(例如从 24 到 2)，它会变得更糟。
Talking-heads 素材通常对帧率不太敏感。
你可以试试setting your bandwidth -- your output bitrate -- explicitly像这样。

-b:v 1000K -maxrate 1200K -bufsize 500K 

这些参数告诉 ffmpeg 给你一个 1 mbps 的恒定速率流，允许一些变化。从您的示例中可以看到类似的内容...

-re -stream_loop -1 -i ${VIDEO_FILE} -vf "fps=${FPS_COMPOSE}"  -b:v 1M  -maxrate 1M -bufsize 500K -f rtsp rtsp://localhost:8554/compose-rtsp

在您的笔记本电脑上尝试各种 ffmpeg 参数组合可能是最简单的，这样您就可以在选择一个放入 docker 镜像之前快速循环各种尝试。