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I am comparing x264 and x265 encoders, with lossless and medium presets. I am so surprised to see below performance results.

| Format             | Size   (KB) | fps  |
|********************|*************|******|
| YUV 420            |   9,182,363 |      |
|                    |             |      |
| x265 (--lossless)  |     442,890 | 1.8  |
| x265 (--medium)    |      12,243 | 2.8  |
|                    |             |      |
| x264 (--lossless)  |     319,139 | 7.2  | 
| x264 (--medium)    |      25,747 | 7.5  |

It raises two questions to me

  1. Why lossless encoding processes less frames per seconds than lossy one? ( I supposed there should be less processing to do)

  2. Why x265 lossless output is much bigger than x264 lossless output? Is this an implementation effect, or related to the HEVC standard?

RawBean
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1 Answers1

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I might try to answer your questions: 1. As you say, the algorithms are different and the lossy is apparently more efficient. 2. This is an implementation effect since both codecs use a different algorithm which differ in speed and size of the output (and internally ram usage, cpu usage etc)

My question back, if you are comparing these, you do that for a reason. The results should provide you the information you need. You can now make en educated quess, so please do so ;)

dmaij
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  • Thanks for your answer, although I was expecting one with more insights ;-) Sorry, but I don't get your point about the educated guess that I make now. I am mainly wondering if there are other codecs with better performance in lossless mode, or if x265 would be improved in the lossless mode. Last, I concluded that if I absolutely need lossless I will choose x264, definitely. – RawBean Mar 03 '16 at 16:14
  • Considering your results, I would too. Good luck! – dmaij Mar 04 '16 at 08:38