soundd: fix audio glitch in get_sound_data when frames < sound length

[Lidang-Jiang]

Summary

Fix boundary condition bug in Soundd.get_sound_data() where current_sound_frame and loops were not recomputed after each chunk write inside the while loop. When the audio callback requested fewer frames than the sound's total length, subsequent callbacks duplicated the tail of the sound instead of wrapping around to the beginning.

• Add per-iteration recomputation of current_sound_frame and loops inside the while loop (2 lines)
• Add 8 regression tests covering wrap-around, single-play stop, multi-callback continuity, and volume scaling

Fixes #36285

Before (bug reproduction)

============================================================
Test: frames=50, sound_data length=70, infinite looping
============================================================

Callback 1 (frames=50):
  current_sound_frame after: 50
  result: [0. 1. 2. 3. 4. 5. 6. 7. 8. 9.]...[45. 46. 47. 48. 49.]
  Correct (should be [0..49]): True

Callback 2 (frames=50):
  current_sound_frame after: 100
  result: [50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67.
 68. 69. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65.
 66. 67. 68. 69. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59.]
  Expected: [50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67.
 68. 69.  0.  1.  2.  3.  4.  5.  6.  7.  8.  9. 10. 11. 12. 13. 14. 15.
 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.]
  Correct (should be [50..69, 0..29]): False

  >>> BUG CONFIRMED: second callback does NOT wrap correctly!
  >>> Got duplicated tail data instead of wrapping to start

============================================================
Test: frames=50, sound_data length=70, single play (num_loops=1)
============================================================

Callback 2 (frames=50):
  current_sound_frame after: 100
  result: [50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67.
 68. 69. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65.
 66. 67. 68. 69. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59.]
  Expected: [50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67.
 68. 69.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.
  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.]
  Correct (should be [50..69, zeros]): False

  >>> BUG CONFIRMED: single-play boundary also broken!

============================================================
SOME TESTS FAILED - BUG CONFIRMED
============================================================

After (bug fixed)

============================================================
Test: frames=50, sound_data length=70, infinite looping
============================================================

Callback 2 (frames=50):
  current_sound_frame after: 100
  result: [50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67.
 68. 69.  0.  1.  2.  3.  4.  5.  6.  7.  8.  9. 10. 11. 12. 13. 14. 15.
 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.]
  Correct (should be [50..69, 0..29]): True

============================================================
Test: frames=50, sound_data length=70, single play (num_loops=1)
============================================================

Callback 2 (frames=50):
  current_sound_frame after: 70
  result: [50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67.
 68. 69.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.
  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.  0.]
  Correct (should be [50..69, zeros]): True

============================================================
ALL TESTS PASSED
============================================================

test_soundd_standalone.py 8 passed in 0.21s

Test plan

• Standalone bug reproduction script (before/after comparison)
• 8 unit tests in test_soundd_standalone.py: boundary wrap, single-play stop, multi-callback stream, silence, volume scaling
• Tests added to selfdrive/ui/tests/test_soundd.py for CI integration

[github-actions]

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✅ 0 changed, 66 passed, 0 errors

[github-actions]

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