# FFmpeg Encode If Needed

FFmpeg wrapper to encode upon some conditions.

## Installation

The script can be use "as is" with a command like `./ffmpeg_ein.sh` but
you could also "install" it with something like:

```bash
mv ffmpeg_ein.sh /usr/bin/ffmpeg_ein
```

## Usage

```bash
ffmpeg_ein [OPTION] [INPUT]
````

Refer to the `-h` argument to get the full list of options.

## Description

By default, FFmpeg encode a file regardless of the fact that the
original and selected codec are the same. Although it may be be a
desired outcome, it can lead to unnecessary operations losing time
and quality.

This script allow the user to specified a desired codec for audio
and video, only if either of those are not present an encoding will be
triggered.

For example if the desired codecs are aac/h264 and the source file is
wmav2/h264 then the file will be encoded with aac and the h264 stream
copied.

| Desired ( `-a aac` ) | Source |   FFmpeg option  |
|:--------------------:|:------:|:----------------:|
|          aac         |   aac  |    `-c:a copy`   |
|          aac         |    X   | content of  `-b` |

**Warning**, by default no output is set, use the `-d` option or specify
the output file with `-o`.

### Batch friendly

This script is designed to be batch friendly allowing the sorting of
processed and sources files within multiple directories. The following
points also help in this endeavor:

+ INPUT can be multiple files and/or directories.
+ The output files will be automatically named with the `-d` option.
+ Errors generated by FFmepg are stored in a *[FILE].error.txt* file
alongside the outputted file.
+ Friendly statistics available if the verbose option is set to default
value.

## Example

```bash
ffmpeg_ein \
-a aac -b "-c:a aac -b:a 48k" \
-v h264 -u "-c:v libx264 -crf 23" \
-d /tmp/ \
[FILE]
```

Will result in the encoding of the file(s) [FILE] if either their audio
codec is not "aac" or their video codec is not "h264". The result
encoded file(s) (if created) will have the same name as the original(s)
and be placed in the "/tmp" folder.

|  Desired  |   Source  |             FFmpeg option              |
|:---------:|:---------:|:--------------------------------------:|
|  aac/h264 |  aac/h264 |           -c:a copy -c:v copy          |
|  aac/h264 |   X/h264  |      -c:a aac -b:a 48k  -c:v copy      |
|  aac/h264 |   aac/X   |         -c:a copy -c:v libx264 -crf 23 |
|  aac/h264 |    X/X    | -c:a aac -b:a 48k -c:v libx264 -crf 23 |

## Limitations / Future roadmap

+ Only the first audio and video streams are accounted for during codec
comparaison.
+ Only the codecs are checked so it's not possible to trigger encoding
on other parameters like bitrate or length.
+ The comparaison doesn't allow for multiple value (example compare
source against h264 and mpeg4)
+ No "-n, --dry-run" option exist to perform a trial run with no
changes made.
+ Some assumptions are made regarding the fact that the user will
provide valid input (valid FFmpeg arguments; read/write access to
specified files and folders; ...)