ffmpeg transcode loss information

I have a system taking videos of various formats as input and transcoding them into the same format for storage and processing and semantic analysis such as object detection.

First, I wonder is this the common strategy employed by companies?

Second, as asked in this question ffmpeg-transcode-twice-loss-information, even when the input video and my system's output video have the exactly same format and encoding parameters/configurations, there would be information loss during the transcoding process.

I'd like to minimize this information loss, which is not due to different codec but due to the second encoding, is there any way to still use lossy transcoding?

Thanks.

apoliver

Posted 2018-12-25T17:44:21.890

Reputation: 11

"I wonder is this the common strategy employed by companies?" – hard to answer. You haven't explained why it is even necessary to encode the video again. What kind of processing are you doing that requires this? Semantic analysis is a read-only operation. If you want to reduce file size, of course, there's no other way than re-encoding. – slhck – 2018-12-26T16:13:00.500

I have a semantic analysis model trained for videos compressed by one specific encoding standard (say 1). But I hope the model also can work as well on videos encoded by other codecs (say 2, 3, ..). Thus I want to transcode them from 2, 3.. back to 1. But I do not want to loss useful information during this transcoding process.. – apoliver – 2018-12-26T16:35:41.630

But the model works on pixel data, not on bitstream data, correct? If you just want to encode without loss, setting -crf 0 for libx264 would, for example, encode to H.264 without any quantization loss. But that's not a very "realistic" encode that you would see in practice. You ideally want to start with uncompressed test content and encode it according to your needs. See https://vqeg.github.io/software-tools/video-databases/

– slhck – 2018-12-28T09:10:56.573

Thanks for your suggestion. I am wondering would it be possible to encode without loss using mepg4 codec (MPEG4 Part2) ? Thank you. – apoliver – 2019-01-03T17:26:54.927

Not that I know of, but I haven't used MPEG-4 Part II video in a long time. – slhck – 2019-01-04T13:51:09.333

ffmpeg transcode loss information

No answers