ffmpeg - 支持转换器的多种文件格式如何工作？

Question

ffmpeg/avconv、imagemagick convert 等软件。

他们是否使用中间格式:

format1 -> I. F.
format2 -> I. F.
I. F. -> format2
I. F. -> format3
...

或者他们是否有一种方法可以在每种支持的格式之间进行转换:

format1 -> format2
format1 -> format3
format2 -> format1
format2 -> format3
...

Answer 1

来自 ffmpeg documentation :

The decoder produces uncompressed frames (raw video/PCM audio/...) which can be processed further by filtering. After filtering, the frames are passed to the encoder, which encodes them and outputs encoded packets. Finally those are passed to the muxer, which writes the encoded packets to the output file.

The transcoding process in ffmpeg for each output can be described by the following diagram:

 _______              ______________
|       |            |              |
| input |  demuxer   | encoded data |   decoder
| file  | ---------> | packets      | -----+
|_______|            |______________|      |
                                           v
                                       _________
                                      |         |
                                      | decoded |
                                      | frames  |
                                      |_________|
 ________             ______________       |
|        |           |              |      |
| output | <-------- | encoded data | <----+
| file   |   muxer   | packets      |   encoder
|________|           |______________|