[FFmpeg-user] Is FLAC lossless for compression_level > 0?

[Jim DeLaHunt]

On 2025-06-08 16:17, Mark Filipak wrote:

> On 08/06/2025 17.06, Jim DeLaHunt wrote:
>> On 2025-06-08 13:35, Mark Filipak wrote:
>>
>>> Is FLAC (Free Lossless Audio Codec) lossless for compression_level > 0?
>>
>> Yes, says the FLAC documentation[1]: it is "an audio format similar 
>> to MP3, but lossless, meaning that audio is compressed in FLAC 
>> without any loss in quality."
> …[elided]…
>> FLAC's documentation of the FLAC stream format[2] says:
>> …[elided]…
>
> I'm reading the so-called specification. It's vague. 

As I read it, [2] is not a so-called "specification", it is a so-called 
"overview". So called in the page title, "Format overview". If you look 
further through the FLAC documentation, you will see that for a "FLAC 
format specification" it refers to RFC 9639[3]. That is the document to 
check for vagueness.


> What is a 'block'? What is a 'frame'? It doesn't say, but it 'sounds' 
> to me like transport, not encoding. Oh, well.
I believe the question here is, "Is FLAC lossless for compression_level 
 > 0?" Is the metaphysics of what part of the FLAC transformation is 
"transport" versus "encoding" helpful to you for answering that 
question?  For me the "format overview" is sufficient to give intuitive 
credibility to the documentations claim that yes, FLAC is lossless, and 
yes, compression_level still has an effect while still being lossless.
>> [1] /FLAC website/, <https://xiph.org/flac/>
>> [2] /FLAC website/, *Format overview* 
>> <https://xiph.org/flac/documentation_format_overview.html>

[3] /RFC 9639 Free Lossless Audio Codec (FLAC)/, 
<https://www.rfc-editor.org/rfc/rfc9639.html>


>
> Thank you, Jim. You have heart.
Why thank you. That is kind.