Readme benchmarks with approximate mode (#515)

Author: scotts

README.md

@@ -207,7 +207,10 @@ The top row is a [Mandelbrot](https://ffmpeg.org/ffmpeg-filters.html#mandelbrot)
 generated from FFmpeg that has a resolution of 1280x720 at 60 fps and is 120 seconds long.
 The bottom row is [promotional video from NASA](https://download.pytorch.org/torchaudio/tutorial-assets/stream-api/NASAs_Most_Scientifically_Complex_Space_Observatory_Requires_Precision-MP4_small.mp4)
 that has a resolution of 960x540 at 29.7 fps and is 206 seconds long. Both videos were
-encoded with libx264 and yuv420p pixel format.
+encoded with libx264 and yuv420p pixel format. All decoders, except for TorchVision, used FFmpeg 6.1.2. TorchVision used FFmpeg 4.2.2.
+
+For TorchCodec, the "approx" label means that it was using [approximate mode](https://pytorch.org/torchcodec/stable/generated_examples/approximate_mode.html)
+for seeking.
 
 ## Planned future work