I used ffmpeg to transcode some files into new format and with certain parameters. After transcoding, I found some output file's metadata is not what I expected, the output value is not the same with I set in the cmd line.
Before transcoding I check the media info of the inputfile:
ffmpeg -i dz2015082000010.mpg
ffmpeg version 3.2.4 Copyright (c) 2000-2017 the FFmpeg developers
built with gcc 4.8.3 (GCC) 20140911 (Red Hat 4.8.3-9)
configuration: --enable-static --enable-memalign-hack --enable-libx264 --enable-gpl --enable-pthreads --enable-version3 --enable-avisynth --enable-bzlib --enable-iconv --enable-zlib --enable-nonfree --extra-cflags=-I/usr/local/include/ --extra-ldflags=-L/usr/local/lib --enable-debug=3 --disable-optimizations --enable-nonfree --enable-libmp3lame libavutil 55. 34.101 / 55. 34.101 libavcodec 57. 64.101 / 57. 64.101 libavformat 57. 56.101 / 57. 56.101 libavdevice 57. 1.100 / 57. 1.100 libavfilter 6. 65.100 / 6. 65.100 libswscale 4. 2.100 / 4. 2.100 libswresample 2. 3.100 / 2. 3.100 libpostproc 54. 1.100 / 54. 1.100 Input #0, mpeg, from 'dz2015082000010.mpg': Duration: 00:01:49.30, start: 0.685389, bitrate: 15723 kb/s
Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, top first), 1920x1080 [SAR 1:1 DAR 16:9], 15000 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
Stream #0:1[0x1c0]: Audio: mp2, 48000 Hz, stereo, s16p, 384 kb/s At least one output file must be specified
Next, transcoding with the cmd line:
ffmpeg -i dz2015082000010.mpg -vcodec libx264 -b:v 4000k -s 1920x1080 -r 25 -g 25 -vprofile main -acodec aac -strict -2 -b:a 128k -ac 2 -ar 44100 -y output.ts
After transcoding, I check the media info of the output file:
ffmpeg -i output.ts
ffmpeg version 3.2.4 Copyright (c) 2000-2017 the FFmpeg developers built with gcc 4.8.3 (GCC) 20140911 (Red Hat 4.8.3-9) configuration: --enable-static --enable-memalign-hack --enable-libx264 --enable-gpl --enable-pthreads --enable-version3 --enable-avisynth --enable-bzlib --enable-iconv --enable-zlib --enable-nonfree --extra-cflags=-I/usr/local/include/ --extra-ldflags=-L/usr/local/lib --enable-debug=3 --disable-optimizations --enable-nonfree --enable-libmp3lame libavutil 55. 34.101 / 55. 34.101 libavcodec 57. 64.101 / 57. 64.101 libavformat 57. 56.101 / 57. 56.101
libavdevice 57. 1.100 / 57. 1.100 libavfilter 6. 65.100 / 6. 65.100 libswscale 4. 2.100 / 4. 2.100
libswresample 2. 3.100 / 2. 3.100 libpostproc 54. 1.100 / 54. 1.100 Input #0, mpegts, from 'full-2.ts': Duration: 00:01:49.30, start: 1.456778, bitrate: 4455 kb/s Program 1
Metadata:
service_name : Service01
service_provider: FFmpeg
Stream #0:0[0x100]: Video: h264 (Main) ([27][0][0][0] / 0x001B), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 90k tbn, 50 tbc
Stream #0:1[0x101]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 4 kb/s At least one output file must be specified
I don't know why the audio bitrate is changed to 4 kb/s after transcoding, I set the value with -b:a 128k before, anybody can help me? BTW, the output file sounds all right.
