Answers.Body: <p>Both h.265 and h.264 are compressed codecs so there will loss; due to compression; whether it's visible to the naked eye or not. </p>
  
  <p>The only way to not lose quality is to output to a lossless codec at 4:4:4. </p>
  
  <p>This results in large files. A common codec for this is Quicktime Animation Codec at 100 Quality. 100% Lossless. </p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-06-07T08:03:21.657Z
Answers.Text: H.264 and H.265 both have lossless modes (@4:2:0/2, not just 4:4:4)
Answers.UserDisplayName: Gyan
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Answers.CreationDate: 2017-06-07T08:28:29.407Z
Answers.Text: I stand corrected then... I have never tried, is this possible from within the adobe platform or is ffmpeg required?
Answers.UserDisplayName: McFlySoHigh
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-06-07T08:37:00.307Z
Answers.Text: ffmpeg and x264/x265 standalone- yes; Adobe - don't know but doubt it.
Answers.UserDisplayName: Gyan
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Answers.CreationDate: 2017-06-07T08:00:53.053Z
Answers.LastActivityDate: 2017-06-07T08:00:53.053Z
Answers.UserDisplayName: McFlySoHigh
Answers.Body: <p>Generally, H.264 and H.265 (as well as others like VP9) are <em>lossy</em> codecs, at least in their default settings with most encoders. This means that whenever you re-encode from one to another (or even in the same codec), you throw away information.</p>
  
  <p>Whether this information loss is visible or not depends on your source material and the chosen settings, of course.</p>
  
  <p>To combat the loss of information, you often need to choose a higher bitrate than what your input is, or a higher constant-quality setting than the default of the respective encoders. There is no "general principle" here – it really depends on what the default bitrates or quality targets are for the encoders you're using.</p>
  
  <blockquote>
    <p>Can I transcode video from h.265 to h.264 without losing quality?</p>
  </blockquote>
  
  <p>Yes, you can. There are two ways to do that, depending on how you define "losing quality":</p>
  
  <ul>
  <li><p>You can enable a lossless mode for these codecs, at least with the x264, x265 or libvpx encoders. This will perform lossless transforms without quantization and disable <a href="https://en.wikipedia.org/wiki/Chroma_subsampling" rel="noreferrer">color subsampling</a> (i.e., 4:4:4 output). The output is mathematically lossless. If you do not have to use H.264 or H.265 specifically, other lossless codecs such as HuffYUV or FFV1 exist.</p></li>
  <li><p>You can try to find the threshold where any (mathematical) quality loss is not visible anymore to human subjects, that is, within the range of a <a href="https://en.wikipedia.org/wiki/Just-noticeable_difference" rel="noreferrer">Just Noticeable Difference</a>. This requires a bit of testing with different settings and repeated viewings. Some codecs are better at this, in terms of their default settings, like ProRes, DNxHD, etc.</p></li>
  </ul>
  
  <p>For more info, read this: <a href="https://superuser.com/questions/1212023/ffmpeg-settings-for-converting-still-images-to-video-for-archival/1212038#1212038">ffmpeg settings for converting still images to video for archival</a></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-06-07T22:45:38.493Z
Answers.Text: You mean "H.264 and H.26*5*" in the first sentence, right?
Answers.UserDisplayName: Michael Liebman
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Answers.CreationDate: 2017-06-08T21:11:25.337Z
Answers.Text: Very informative.  I'm curious to see what the file size difference will be if I convert from lossy to lossless.  I suspect I'll be visually looking for that threshold you mention.
Answers.UserDisplayName: John
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Answers.CreationDate: 2019-02-08T22:40:47.060Z
Answers.Text: that ffmpeg settings link has really good info, thx vm!
Answers.UserDisplayName: Aquarius Power
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Answers.UserDisplayName: slhck
Body: <p>Can I transcode video from h.265 to h.264 without loosing quality?</p>
  
  <p>My instinct is that it should be fine, that with approximate quality settings the new files will be the same quality but larger file size.  Or am I wrong, does transcoding from one codec to another follow the principle of "copy of a copy always means lower quality"?</p>
  
Tags: <video-quality><conversion>
Title: Does transcoding always mean quality loss?
UserDisplayName: John
ThreadText: # Does transcoding always mean quality loss?
  
  (Asked by: username_0 on 2017-06-07)
  
  Can I transcode video from h.265 to h.264 without loosing quality?
  
  My instinct is that it should be fine, that with approximate quality settings the new files will be the same quality but larger file size. Or am I wrong, does transcoding from one codec to another follow the principle of "copy of a copy always means lower quality"?
  
  **Tags:** video-quality, conversion
  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_3 on 2017-06-07. Score: 8 | Accepted answer
  
  Generally, H.264 and H.265 (as well as others like VP9) are *lossy* codecs, at least in their default settings with most encoders. This means that whenever you re-encode from one to another (or even in the same codec), you throw away information.
  
  Whether this information loss is visible or not depends on your source material and the chosen settings, of course.
  
  To combat the loss of information, you often need to choose a higher bitrate than what your input is, or a higher constant-quality setting than the default of the respective encoders. There is no "general principle" here – it really depends on what the default bitrates or quality targets are for the encoders you're using.
  
  > Can I transcode video from h.265 to h.264 without losing quality?
  
  Yes, you can. There are two ways to do that, depending on how you define "losing quality":
  
  * You can enable a lossless mode for these codecs, at least with the x264, x265 or libvpx encoders. This will perform lossless transforms without quantization and disable [color subsampling](https://en.wikipedia.org/wiki/Chroma_subsampling) (i.e., 4:4:4 output). The output is mathematically lossless. If you do not have to use H.264 or H.265 specifically, other lossless codecs such as HuffYUV or FFV1 exist.
  * You can try to find the threshold where any (mathematical) quality loss is not visible anymore to human subjects, that is, within the range of a [Just Noticeable Difference](https://en.wikipedia.org/wiki/Just-noticeable_difference). This requires a bit of testing with different settings and repeated viewings. Some codecs are better at this, in terms of their default settings, like ProRes, DNxHD, etc.
  
  For more info, read this: [ffmpeg settings for converting still images to video for archival](https://superuser.com/questions/1212023/ffmpeg-settings-for-converting-still-images-to-video-for-archival/1212038#1212038)
  
  > **Comments:**
  > **username_4**: You mean "H.264 and H.26*5*" in the first sentence, right?  
  > **username_0**: Very informative.  I'm curious to see what the file size difference will be if I convert from lossy to lossless.  I suspect I'll be visually looking for that threshold you mention.  
  > **username_5**: that ffmpeg settings link has really good info, thx vm!  
  
  ---
  
  ### Answer by username_1 on 2017-06-07. Score: 0
  
  Both h.265 and h.264 are compressed codecs so there will loss; due to compression; whether it's visible to the naked eye or not.
  
  The only way to not lose quality is to output to a lossless codec at 4:4:4.
  
  This results in large files. A common codec for this is Quicktime Animation Codec at 100 Quality. 100% Lossless.
  
  > **Comments:**
  > **username_2**: H.264 and H.265 both have lossless modes (@4:2:0/2, not just 4:4:4)  
  > **username_1**: I stand corrected then... I have never tried, is this possible from within the adobe platform or is ffmpeg required?  
  > **username_2**: ffmpeg and x264/x265 standalone- yes; Adobe - don't know but doubt it.  
  
  ---
  
  