如何从命令行成功将 .3g2 转换为 .mp4？我使用如下 ffmpeg 命令：
ffmpeg -i input.3g2 -acodec copy -vcodec libx264 output.mp4
ffmpeg -i input.3g2 -acodec ac3 -vcodec libx264 output.mp4
这些命令会产生视频，但不会产生音频。以下是 ffmpeg 的输出：
ffmpeg -i input.3g2 -acodec ac3 -vcodec libx264 input.mp4
ffmpeg version 0.10.2.git Copyright (c) 2000-2012 the FFmpeg developers
built on Jun 13 2012 05:18:13 with gcc 4.4.5
configuration: --enable-gpl --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264 --enable-nonfree --enable-version3
libavutil 51. 58.100 / 51. 58.100
libavcodec 54. 25.100 / 54. 25.100
libavformat 54. 6.101 / 54. 6.101
libavdevice 54. 0.100 / 54. 0.100
libavfilter 2. 78.101 / 2. 78.101
libswscale 2. 1.100 / 2. 1.100
libswresample 0. 15.100 / 0. 15.100
libpostproc 52. 0.100 / 52. 0.100
Guessed Channel Layout for Input Stream #0.1 : mono
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output.3g2':
Metadata:
major_brand : 3g2a
minor_version : 0
compatible_brands: 3g2a
creation_time : 2006-02-03 22:54:07
Duration: 00:00:15.14, start: 0.000000, bitrate: 94 kb/s
Stream #0:0(eng): Video: mpeg4 (Simple Profile) (mp4v / 0x7634706D), yuv420p, 176x144 [SAR 1:1 DAR 11:9], 79 kb/s, SAR 12:11 DAR 4:3, 15 fps, 15 tbr, 15 tbn, 15 tbc
Metadata:
creation_time : 2006-02-03 22:54:07
handler_name : VideoHandler
Stream #0:1(eng): Audio: qcelp (mp4a / 0x6134706D), 8000 Hz, mono, flt, 14 kb/s
Metadata:
creation_time : 2006-02-03 22:54:07
handler_name : AudioHandler
[buffer @ 0xa820b40] w:176 h:144 pixfmt:yuv420p tb:1/15 fr:15/1 sar:12/11 sws_param:flags=2
[ffmpeg_buffersink @ 0xa820ea0] No opaque field provided
[libx264 @ 0xa81fb00] using SAR=12/11
[libx264 @ 0xa81fb00] using cpu capabilities: MMX2 SSE2Fast SSSE3 Cache64
[libx264 @ 0xa81fb00] profile High, level 1.0
[libx264 @ 0xa81fb00] 264 - core 118 - H.264/MPEG-4 AVC codec - Copyleft 2003-2011 - 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=6 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=15 scenecut=40 Output #0, mp4, to 'output.mp4':
Metadata:
major_brand : 3g2a
minor_version : 0
compatible_brands: 3g2a
creation_time : 2006-02-03 22:54:07
encoder : Lavf54.6.101
Stream #0:0(eng): Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 176x144 [SAR 12:11 DAR 4:3], q=-1--1, 15 tbn, 15 tbc
Metadata:
creation_time : 2006-02-03 22:54:07
handler_name : VideoHandler
Stream #0:1(eng): Audio: ac3 ([165][0][0][0] / 0x00A5), 8000 Hz, mono, flt, 96 kb/s
Metadata:
creation_time : 2006-02-03 22:54:07
handler_name : AudioHandler
Stream mapping:
Stream #0:0 -> #0:0 (mpeg4 -> libx264)
Stream #0:1 -> #0:1 (qcelp -> ac3)
Press [q] to stop, [?] for help
frame= 225 fps=214 q=-1.0 Lsize= 327kB time=00:00:14.86 bitrate= 180.4kbits/s
video:146kB audio:178kB global headers:0kB muxing overhead 0.950448%
[libx264 @ 0xa81fb00] frame I:1 Avg QP:23.26 size: 1021
[libx264 @ 0xa81fb00] frame P:218 Avg QP:23.35 size: 671
[libx264 @ 0xa81fb00] frame B:6 Avg QP:26.62 size: 356
[libx264 @ 0xa81fb00] consecutive B-frames: 95.1% 3.6% 1.3% 0.0%
[libx264 @ 0xa81fb00] mb I I16..4: 11.1% 87.9% 1.0%
[libx264 @ 0xa81fb00] mb P I16..4: 0.8% 7.4% 0.2% P16..4: 64.1% 17.4% 6.0% 0.0% 0.0% skip: 4.1%
[libx264 @ 0xa81fb00] mb B I16..4: 0.8% 5.2% 0.2% B16..8: 52.4% 10.4% 1.3% direct: 2.7% skip:26.9% L0:68.5% L1:21.0% BI:10.5%
[libx264 @ 0xa81fb00] 8x8 transform intra:88.3% inter:83.3%
[libx264 @ 0xa81fb00] coded y,uvDC,uvAC intra: 78.7% 80.3% 16.7% inter: 36.2% 30.9% 0.7%
[libx264 @ 0xa81fb00] i16 v,h,dc,p: 16% 12% 55% 17%
[libx264 @ 0xa81fb00] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 23% 18% 37% 3% 3% 3% 5% 4% 4%
[libx264 @ 0xa81fb00] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 30% 14% 18% 3% 8% 9% 6% 10% 2%
[libx264 @ 0xa81fb00] i8c dc,h,v,p: 58% 16% 19% 6%
[libx264 @ 0xa81fb00] Weighted P-Frames: Y:3.2% UV:0.0%
[libx264 @ 0xa81fb00] ref P L0: 78.6% 15.8% 4.3% 1.2% 0.1%
[libx264 @ 0xa81fb00] ref B L0: 93.0% 6.4% 0.6%
[libx264 @ 0xa81fb00] ref B L1: 98.4% 1.6%
[libx264 @ 0xa81fb00] kb/s:79.65
ffprobe 输出：
ffprobe version 0.10.2.git Copyright (c) 2007-2012 the FFmpeg developers
built on Jun 13 2012 05:18:13 with gcc 4.4.5
configuration: --enable-gpl --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264 --enable-nonfree --enable-version3
libavutil 51. 58.100 / 51. 58.100
libavcodec 54. 25.100 / 54. 25.100
libavformat 54. 6.101 / 54. 6.101
libavdevice 54. 0.100 / 54. 0.100
libavfilter 2. 78.101 / 2. 78.101
libswscale 2. 1.100 / 2. 1.100
libswresample 0. 15.100 / 0. 15.100
libpostproc 52. 0.100 / 52. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
creation_time : 2006-02-03 22:54:07
encoder : Lavf54.6.101
Duration: 00:00:15.16, start: 0.000000, bitrate: 176 kb/s
Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 176x144 [SAR 12:11 DAR 4:3], 80 kb/s, 15 fps, 15 tbr, 15 tbn, 30 tbc
Metadata:
creation_time : 2006-02-03 22:54:07
handler_name : VideoHandler
Stream #0:1(eng): Audio: ac3 (ac[45]3 / 0x332D6361), 8000 Hz, mono, s16, 96 kb/s
Metadata:
creation_time : 2006-02-03 22:54:07
handler_name : SoundHandler
psimon@zebra:~/tmp/convert_video$
ffprobe version 0.10.2.git Copyright (c) 2007-2012 the FFmpeg developers
built on Jun 13 2012 05:18:13 with gcc 4.4.5
configuration: --enable-gpl --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264 --enable-nonfree --enable-version3
libavutil 51. 58.100 / 51. 58.100
libavcodec 54. 25.100 / 54. 25.100
libavformat 54. 6.101 / 54. 6.101
libavdevice 54. 0.100 / 54. 0.100
libavfilter 2. 78.101 / 2. 78.101
libswscale 2. 1.100 / 2. 1.100
libswresample 0. 15.100 / 0. 15.100
libpostproc 52. 0.100 / 52. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
creation_time : 2006-02-03 22:54:07
encoder : Lavf54.6.101
Duration: 00:00:15.16, start: 0.000000, bitrate: 176 kb/s
Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 176x144 [SAR 12:11 DAR 4:3], 80 kb/s, 15 fps, 15 tbr, 15 tbn, 30 tbc
Metadata:
creation_time : 2006-02-03 22:54:07
handler_name : VideoHandler
Stream #0:1(eng): Audio: ac3 (ac[45]3 / 0x332D6361), 8000 Hz, mono, s16, 96 kb/s
Metadata:
creation_time : 2006-02-03 22:54:07
handler_name : SoundHandler
答案1
来自文档官方MP4注册机构，似乎不支持 QCELP。但是 AC-3 是支持的。[45]inac[45]3 是破折号的 ASCII 码，也就是ac-3，这是 MP4 的有效编解码器。因此，似乎文件本身是有效的，否则 FFmpeg 会抱怨。
我猜想是 QuickTime 本身无法将文件读取为 MP4。您可以尝试按照建议将扩展名更改为 M4V这里或者这里或者尝试编码为 MOV 容器，这对 QuickTime 来说更为原生。
再说一次，如果您编码为 h.264 / AAC 音频，您将获得与 MP4 的最佳兼容性，它将是这样的：
ffmpeg -i input.3g2 -c:v libx264 -c:a libfaac out.mp4
AAC 编码器采用各种参数，最值得注意的是：
-ar 44100作为采样率-ac 2作为音频通道数（使用 1 表示单声道）-b:a