Repository: yt-dlp
Issue: Bilibili - Can't `-f bv,ba` because `ba` is also written into mp4. So after downloading `bv` , downloading `ba` fails.
Labels: site-bug,patch-available,needs-testing

### DO NOT REMOVE OR SKIP THE ISSUE TEMPLATE

- [X] I understand that I will be **blocked** if I *intentionally* remove or skip any mandatory\* field

### Checklist

- [X] I'm reporting that yt-dlp is broken on a **supported** site
- [X] I've verified that I have **updated yt-dlp to nightly or master** ([update instructions](https://github.com/yt-dlp/yt-dlp#update-channels))
- [X] I've checked that all provided URLs are playable in a browser with the same IP and same login details
- [X] I've checked that all URLs and arguments with special characters are [properly quoted or escaped](https://github.com/yt-dlp/yt-dlp/wiki/FAQ#video-url-contains-an-ampersand--and-im-getting-some-strange-output-1-2839-or-v-is-not-recognized-as-an-internal-or-external-command)
- [X] I've searched [known issues](https://github.com/yt-dlp/yt-dlp/issues/3766) and the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues **including closed ones**. DO NOT post duplicates
- [X] I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)
- [ ] I've read about [sharing account credentials](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#are-you-willing-to-share-account-details-if-needed) and I'm willing to share it if required

### Region

_No response_

### Provide a description that is worded well enough to be understood

The current behavior is fine for `bv+ba` which automatically adds `%(format_id)s` to filename during download, but I like to use `-f bv,ba` and downloading `ba` fails because yt-dlp thinks the file is already downloaded, as the filename already exists and `bv` content-length typically exceeds `ba` content-length .

I prefer to archive stuff unmuxed.

I'm aware that I could manually add `%(format_id)s` to my `-o` but I'd prefer not to.

Please fix it so that yt-dlp downloads audio only formats from bilibili to non `.mp4` file.

Maybe m4a? Since the audio is aac?

    Stream #0:0[0x2](und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 5 kb/s (default)

Thanks.


### Provide verbose output that clearly demonstrates the problem

- [X] Run **your** yt-dlp command with **-vU** flag added (`yt-dlp -vU <your command line>`)
- [ ] If using API, add `'verbose': True` to `YoutubeDL` params instead
- [X] Copy the WHOLE output (starting with `[debug] Command-line config`) and insert it below

### Complete Verbose Output

```shell
$ yt-dlp -v --no-config --fixup warn -S tbr -f bv,ba https://www.bilibili.tv/en/video/4792404558745600
[debug] Command-line config: ['-v', '--no-config', '--fixup', 'warn', '-S', 'tbr', '-f', 'bv,ba', 'https://www.bilibili.tv/en/video/4792404558745600']
[debug] yt-dlp version nightly@2024.08.21.232751 from yt-dlp/yt-dlp-nightly-builds [6f9e65374] (win_exe)
[debug] Python 3.8.10 (CPython AMD64 64bit) - Windows-7-6.1.7601-SP1 (OpenSSL 1.1.1k  25 Mar 2021)
[debug] exe versions: ffmpeg 7.0-full_build-www.gyan.dev (setts), ffprobe 7.0-full_build-www.gyan.dev
[debug] Optional libraries: Cryptodome-3.20.0, brotli-1.1.0, certifi-2024.07.04, curl_cffi-0.5.10, mutagen-1.47.0, requests-2.32.3, sqlite3-3.35.5, urllib3-2.2.2, websockets-13.0
[debug] Request Handlers: urllib, requests, websockets, curl_cffi
[debug] Extractor Plugins: AGB (YoutubeIE), Youtube_AgeGateBypassIE
[debug] Loaded 1831 extractors
[BiliIntl] Extracting URL: https://www.bilibili.tv/en/video/4792404558745600
[BiliIntl] 4792404558745600: Downloading webpage
[BiliIntl] 4792404558745600: Downloading video formats
[debug] Sort order given by user: tbr
[debug] Formats sorted by: hasvid, ie_pref, tbr, lang, quality, res, fps, hdr:12(7), vcodec:vp9.2(10), channels, acodec, size, br, asr, proto, vext, aext, hasaud, source, id
[info] 4792404558745600: Downloading 2 format(s): 9, 1
[debug] Invoking http downloader on "https://upos-bstar1-mirrorakam.akamaized.net/bestvideoURL"
[debug] File locking is not supported. Proceeding without locking
[download] Destination: sayang namatay din [4792404558745600].mp4
[download] 100% of    6.00MiB in 00:00:13 at 469.15KiB/s
[debug] Invoking http downloader on "https://upos-bstar1-mirrorakam.akamaized.net/bestaudioURL"
[download] sayang namatay din [4792404558745600].mp4 has already been downloaded
[download] 100% of    6.00MiB
```