Lossless describes preserving the encoded source samples after decoding; lossy compression discards some information to reduce data. Neither label guarantees a particular speaker layout, loudness or listening result. The source and complete output chain determine what is actually available. Ask what source was encoded and what reaches the speakers, rather than using the label as a complete quality score. A lossless track can be stereo, a compressed track can be multichannel, and either can be altered by later mixing, processing or an incompatible route.
Separate codec and channels
Stereo can be lossless, and surround can be compressed. Codec family and compression method describe different things from speaker arrangement. Check the actual track information for channel layout, rate and format, and keep that separate from the receiver's listening mode. A stereo input expanded by a virtualizer has not become an original multichannel recording. Similarly, a multichannel lossy track does not lose its channel identity simply because its coding discards some waveform information. Use the labels for the properties they actually describe.
Check transport support
Some high-bandwidth formats need a compatible connection. Read the supported carrier and connection requirements for the selected track. A decoder may understand a format that an intermediate TV or return link cannot pass unchanged. Source decoding to supported PCM can be an alternative, but channel count and layout still need checking. The destination's received-format information can help confirm the active route. Avoid buying a cable solely on a lossless badge without first verifying that both endpoints support the required signal on that input.
Avoid conversion myths
Converting a lossy track to PCM does not restore discarded source information. Decoding a lossy source normally produces PCM for playback, but this representation does not reverse information discarded during the original compression. Saving that PCM in a lossless file preserves the decoded result, not an unavailable original master. Judge actual dialogue clarity, noise and balance at matched comfortable levels. A louder playback mode or larger file is not sufficient evidence that detail was recovered, and source mastering differences can matter more than a simple codec label.
A practical sequence
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An example to work through
A decoded compressed track is output as PCM, but its original compression history has not disappeared. A receiver reports PCM after the source decodes a compressed track. That does not prove the original was lossless; it identifies the representation arriving at that stage, while the earlier compression history and the supplied channel layout remain separate questions.
Questions about this topic
DoesPCM always mean original lossless?
No. PCM can be the decoded output of an earlier lossy source as well.
Does lossless guarantee louder dialogue?
No. Dialogue level depends on the mix, routing and processing, not solely on compression classification.
