[FFmpeg-user] Yes or No? About the processing pipeline.

[hydra3333 at gmail.com]

-----Original Message-----
From: ffmpeg-user <ffmpeg-user-bounces at ffmpeg.org> On Behalf Of Paul B Mahol
Sent: Wednesday, June 18, 2025 4:25 PM
To: FFmpeg user questions <ffmpeg-user at ffmpeg.org>
Subject: Re: [FFmpeg-user] Yes or No? About the processing pipeline.

On Tue, Jun 17, 2025 at 11:19 PM Mark Filipak <
markfilipak.imdb-at-gmail.com at ffmpeg.org> wrote:

> On 17/06/2025 12.50, Paul B Mahol wrote:
> > On Tue, Jun 17, 2025 at 4:18 PM Mark Filipak <
> > markfilipak.imdb-at-gmail.com at ffmpeg.org> wrote:
> >
> >> Yes (true) or No (false)?
> >>
> >> If the input is 8-bit ybr420-smpte170m, then the processing pipeline is
> >> also 8-bit ybr420-smpte170m.
> >
> > There is no such thing like ybr420.
>
> You know what? You're right! Ha, ha, ha!
>
> When I read Jim DeLaHunt's treatise on framing and saw "rgb420" in it, I
> thought "Huh"?
>
> I apologize for the error, Paul. I started with a statement about ybr420
> and got sidetracked when I
> succumbed to an impulse to add a second (bogus) example. I sabotaged
> myself.
>
> I do apologize.
>
> Maybe you can tell me why this experiment fails.
>
> ffmpeg^
>   -i "c:\8-bit ybr420 smpte170m.mkv"^
>   -map 0 -c:v libx264 -c:a copy^
>   "c:\8-bit ybr420 smpte170m.mp4"
>
> ffmpeg version N-119869-g3ac7d70291-20250611 Copyright (c) 2000-2025 the
> FFmpeg developers
>    built with gcc 15.1.0 (crosstool-NG 1.27.0.42_35c1e72)
>    configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static
> --pkg-config=pkg-config
> --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32
> --enable-gpl --enable-version3
> --disable-debug --enable-shared --disable-static --disable-w32threads
> --enable-pthreads
> --enable-iconv --enable-zlib --enable-libfribidi --enable-gmp
> --enable-libxml2 --enable-lzma
> --enable-fontconfig --enable-libharfbuzz --enable-libfreetype
> --enable-libvorbis --enable-opencl
> --disable-libpulse --enable-libvmaf --disable-libxcb --disable-xlib
> --enable-amf --enable-libaom
> --enable-libaribb24 --enable-avisynth --enable-chromaprint
> --enable-libdav1d --enable-libdavs2
> --enable-libdvdread --enable-libdvdnav --disable-libfdk-aac
> --enable-ffnvcodec --enable-cuda-llvm
> --enable-frei0r --enable-libgme --enable-libkvazaar
> --enable-libaribcaption --enable-libass
> --enable-libbluray --enable-libjxl --enable-libmp3lame --enable-libopus
> --enable-librist
> --enable-libssh --enable-libtheora --enable-libvpx --enable-libwebp
> --enable-libzmq --enable-lv2
> --enable-libvpl --enable-openal --enable-liboapv
> --enable-libopencore-amrnb
> --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg
> --enable-libopenmpt
> --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2
> --enable-libsnappy
> --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame
> --enable-libuavs3d
> --disable-libdrm --enable-vaapi --enable-libvidstab --enable-vulkan
> --enable-libshaderc
> --enable-libplacebo --enable-libvvenc --enable-libx264 --enable-libx265
> --enable-libxavs2
> --enable-libxvid --enable-libzimg --enable-libzvbi
> --extra-cflags=-DLIBTWOLAME_STATIC
> --extra-cxxflags= --extra-libs=-lgomp --extra-ldflags=-pthread
> --extra-ldexeflags=
> --cc=x86_64-w64-mingw32-gcc --cxx=x86_64-w64-mingw32-g++
> --ar=x86_64-w64-mingw32-gcc-ar
> --ranlib=x86_64-w64-mingw32-gcc-ranlib --nm=x86_64-w64-mingw32-gcc-nm
> --extra-version=20250611
>    libavutil      60.  3.100 / 60.  3.100
>    libavcodec     62.  3.101 / 62.  3.101
>    libavformat    62.  1.100 / 62.  1.100
>    libavdevice    62.  0.100 / 62.  0.100
>    libavfilter    11.  0.100 / 11.  0.100
>    libswscale      9.  0.100 /  9.  0.100
>    libswresample   6.  0.100 /  6.  0.100
> Input #0, matroska,webm, from 'c:\8-bit ybr420 smpte170m.mkv':
>    Metadata:
>      creation_time   : 2025-06-15T04:54:18.000000Z
>      ENCODER         : Lavf58.29.100
>    Duration: 01:59:25.20, start: 0.000000, bitrate: 666 kb/s
>    Stream #0:0: Video: mpeg2video (Main), yuv420p(tv, smpte170m,
> progressive), 720x480 [SAR 32:27
> DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn (default)
>      Metadata:
>        DURATION        : 01:59:25.200000000
>      Side data:
>        cpb: bitrate max/min/avg: 0/0/0 buffer size: 49152 vbv_delay: N/A
>    Stream #0:1: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s, Start
> 0.004000 (default)
>      Metadata:
>        title           : Surround
>        DURATION        : 01:59:25.188000000
>    Stream #0:2: Subtitle: dvd_subtitle (dvdsub), 720x480
>      Metadata:
>        DURATION        : 01:52:11.916000000
> [sost#0:2 @ 0000000004c5ec80] Automatic encoder selection failed Default
> encoder for format mp4
> (codec none) is probably disabled. Please choose an encoder manually.
>
> You need to select video encoder manually because it failed to pick one for
> you automatically.

> [sost#0:2 @ 0000000004c5ec80] Error selecting an encoder
> Error opening output file c:\8-bit ybr420 smpte170m.mp4.
> Error opening output files: Encoder not found

Well,

> ffmpeg^
>   -i "c:\8-bit ybr420 smpte170m.mkv"^
>   -map 0 -c:v libx264 -c:a copy^
>   "c:\8-bit ybr420 smpte170m.mp4"

Perhaps no subtitle encoder specified ?

ChatGPT says:
> The FFmpeg option -map 0 is used to explicitly include all streams (video, audio, subtitles, metadata, etc.) from the first input file (index 0) in the output.
> What does -map 0 mean exactly?
> -map 0 says:
> Include all streams from the first input (0) in the output.
> This includes:
> All video streams
> All audio streams
> All subtitle streams
> Any data or attachment streams
> Even chapters and metadata

And your log seems to indicate subtitles are present.

Just a thought, I am likely wrong.