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FFmpeg Early Probe Explanation

When you open media, a series of libraries and codec functions are used to probe the data, to see if it can determine the type of file format and codec parameters needed to correctly decode the file. If ffmpeg probes early – Try FFMpeg first is in effect for the FF button (green icon) – it will usually find some way to try to decode just about any contemporary media file. But there are some times that the built in codecs are actually a better choice. A lot of this may fall into the category of personal preference. For example, some may prefer the mpeg library in the CINELERRA-GG code over the ffmpeg code because it has more decoding capability and seems to be more robust when the media is damaged. In that case you will want the FF button to read Try FFMpeg last.

To summarize, if ffmpeg probes early, you will never get to use the built in libraries, and if you want to skip over buggy old libraries, use ffmpeg early probe enabled so that the newest code will be tried first. The green icon is located in the upper right hand corner of the main window.

When the icon is green, ffmpeg probes early is enabled and you will see it reads Currently: Try FFMpeg first when moving over the icon button in the upper right hand corner of the screen. When the icon is capital "C", ffmpeg probes early is disabled so that ffmpeg probes late and it reads Currently: Try FFMpeg last. The initial default state of the icon is on, that is, ffmpeg probes first. Suggestion is to leave it on except in a few special cases where it may be better to have early probes disabled. When you mouse over the main menu icon toggle button, the text displays ffmpeg's Currently set position. Just left mouse click to change to the other setting. The ffmpeg early probe state is saved between sessions and is also affected by choices made in Probe Order (refer to section Probe Order when Loading Media). It is important to note that the various file indexes may need to be rebuilt if you change which codec is being used to decode the file. There is a warning popup to remind you when you change the default ffmpeg early probe state (unless you have checked the box to no longer show the warning). You can easily rebuild the index for a specific media file by going to the Resources window, right mouse click on that media, and choose Rebuild Index from the popup choices.

Figure 9.1 shows (1) greenish colored icon in upper right hand corner of main window indicating that ffmpeg early probes is enabled; (2) Try FFMpeg last indicator message for ffmpeg early probes enabled (note that the icon is different because you highlighted the icon); and (3) "C" icon indicates ffmpeg will be used last and you are changing the behavior so that CINELERRA-GG warns you accordingly.

Figure 9.1: The three icons of FF Probe